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• Ffmpeg error "avcodec_send_frame" return "invalid argument"

  17 octobre 2023, par Paulo Coutinho

  I have a problem in function avcodec_send_frame throwing error Error sending frame for encoding: Invalid argument (-22). I already search, check, recheck and nothing. It is near the ffmpeg examples. Can anyone help me ? Thanks.

  


  This is my code :

  


  static void callbackAddSubtitle(const Message &m, const Response r)
{
    try
    {
        av_log_set_level(AV_LOG_DEBUG);

        spdlog::debug("[Mapping :: callbackAddSubtitle] Adding subtitle...");

        auto inputOpt = m.get("input");
        auto outputOpt = m.get("output");

        if (!inputOpt.has_value() || !outputOpt.has_value())
        {
            r(std::string{"INVALID-PARAMS"});
            return;
        }

        const std::string &input = inputOpt.value();
        const std::string &output = outputOpt.value();

        // initialize input
        spdlog::debug("[Mapping :: callbackAddSubtitle] Initializing input video...");

        AVFormatContext *inputFormatCtx = avformat_alloc_context();
        if (avformat_open_input(&inputFormatCtx, input.c_str(), nullptr, nullptr) != 0)
        {
            spdlog::error("Failed to open input");
            r(std::string{"ERROR-OPEN-INPUT"});
            return;
        }

        if (avformat_find_stream_info(inputFormatCtx, nullptr) < 0)
        {
            spdlog::error("Failed to find stream information");
            avformat_close_input(&inputFormatCtx);
            r(std::string{"ERROR-FIND-STREAM"});
            return;
        }

        int videoStreamIndex = av_find_best_stream(inputFormatCtx, AVMEDIA_TYPE_VIDEO, -1, -1, nullptr, 0);
        if (videoStreamIndex < 0)
        {
            spdlog::error("Could not find a video stream");
            r(std::string{"ERROR-FIND-VIDEO-STREAM"});
            return;
        }

        AVRational timeBase = inputFormatCtx->streams[videoStreamIndex]->time_base;

        AVCodecParameters *inputCodecPar = inputFormatCtx->streams[videoStreamIndex]->codecpar;
        const AVCodec *inputCodec = avcodec_find_decoder(inputCodecPar->codec_id);
        AVCodecContext *inputCodecCtx = avcodec_alloc_context3(inputCodec);

        avcodec_parameters_to_context(inputCodecCtx, inputCodecPar);
        avcodec_open2(inputCodecCtx, inputCodec, nullptr);

        // initialize input audio
        spdlog::debug("[Mapping :: callbackAddSubtitle] Initializing input audio...");

        int audioStreamIndex = av_find_best_stream(inputFormatCtx, AVMEDIA_TYPE_AUDIO, -1, -1, nullptr, 0);
        if (audioStreamIndex < 0)
        {
            spdlog::error("Could not find an audio stream");
            r(std::string{"ERROR-FIND-AUDIO-STREAM"});
            return;
        }

        AVCodecParameters *inputAudioCodecPar = inputFormatCtx->streams[audioStreamIndex]->codecpar;
        const AVCodec *inputAudioCodec = avcodec_find_decoder(inputAudioCodecPar->codec_id);
        AVCodecContext *inputAudioCodecCtx = avcodec_alloc_context3(inputAudioCodec);

        avcodec_parameters_to_context(inputAudioCodecCtx, inputAudioCodecPar);
        avcodec_open2(inputAudioCodecCtx, inputAudioCodec, nullptr);

        // initialize output video
        spdlog::debug("[Mapping :: callbackAddSubtitle] Initializing output video...");

        AVFormatContext *outputFormatCtx = nullptr;
        avformat_alloc_output_context2(&outputFormatCtx, nullptr, nullptr, output.c_str());
        AVStream *outputStream = avformat_new_stream(outputFormatCtx, nullptr);

        AVCodecContext *outputCodecCtx = avcodec_alloc_context3(inputCodec);
        avcodec_parameters_to_context(outputCodecCtx, inputCodecPar);
        int retOutVideo = avcodec_open2(outputCodecCtx, inputCodec, nullptr);

        if (retOutVideo < 0)
        {
            char err[AV_ERROR_MAX_STRING_SIZE];
            av_make_error_string(err, AV_ERROR_MAX_STRING_SIZE, retOutVideo);
            spdlog::error("Failed to initialize output video: {}", err);
            r(std::string{"ERROR-INIT-OUTPUT-VIDEO"});
            return;
        }

        outputStream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
        outputStream->codecpar->codec_id = inputCodec->id;
        avcodec_parameters_from_context(outputStream->codecpar, outputCodecCtx);

        if (!(outputFormatCtx->oformat->flags & AVFMT_NOFILE))
        {
            avio_open(&outputFormatCtx->pb, output.c_str(), AVIO_FLAG_WRITE);
        }

        const char *pixelFormatName = getPixelFormatName(outputCodecCtx->pix_fmt);
        spdlog::debug("Pixel Format: {}", pixelFormatName);

        // initialize output audio
        spdlog::debug("[Mapping :: callbackAddSubtitle] Initializing output audio...");

        AVStream *outputAudioStream = avformat_new_stream(outputFormatCtx, nullptr);
        AVCodecContext *outputAudioCodecCtx = avcodec_alloc_context3(inputAudioCodec);
        avcodec_parameters_to_context(outputAudioCodecCtx, inputAudioCodecPar);
        int retOutAudio = avcodec_open2(outputAudioCodecCtx, inputAudioCodec, nullptr);

        if (retOutAudio < 0)
        {
            char err[AV_ERROR_MAX_STRING_SIZE];
            av_make_error_string(err, AV_ERROR_MAX_STRING_SIZE, retOutAudio);
            spdlog::error("Failed to initialize output audio: {}", err);
            r(std::string{"ERROR-INIT-OUTPUT-AUDIO"});
            return;
        }

        outputAudioStream->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
        outputAudioStream->codecpar->codec_id = inputAudioCodec->id;
        avcodec_parameters_from_context(outputAudioStream->codecpar, outputAudioCodecCtx);

        // initialize filters
        spdlog::debug("[Mapping :: callbackAddSubtitle] Initializing filters...");

        AVFilterGraph *filterGraph = avfilter_graph_alloc();
        if (!filterGraph)
        {
            spdlog::error("Failed to allocate filter graph");
            r(std::string{"ERROR-FILTER-GRAPH"});
            return;
        }

        AVFilterContext *bufferSinkCtx;
        AVFilterContext *bufferSrcCtx;

        const AVFilter *bufferSink = avfilter_get_by_name("buffersink");
        const AVFilter *bufferSrc = avfilter_get_by_name("buffer");

        // input filter
        char filterInArgs[512];
        snprintf(filterInArgs, sizeof(filterInArgs), "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d", inputCodecPar->width, inputCodecPar->height, inputCodecCtx->pix_fmt, timeBase.num, timeBase.den, inputCodecCtx->sample_aspect_ratio.num, inputCodecCtx->sample_aspect_ratio.den);

        spdlog::debug("[Mapping :: callbackAddSubtitle] Buffer src args: {}", filterInArgs);

        int retFilterIn = avfilter_graph_create_filter(&bufferSrcCtx, bufferSrc, "in", filterInArgs, nullptr, filterGraph);
        if (retFilterIn < 0)
        {
            char err[AV_ERROR_MAX_STRING_SIZE];
            av_make_error_string(err, AV_ERROR_MAX_STRING_SIZE, retFilterIn);
            spdlog::error("Failed to create bufferSrcCtx: {}", err);
            r(std::string{"ERROR-CREATE-FILTER-SRC"});
            return;
        }

        // output filter
        int retFilterOut = avfilter_graph_create_filter(&bufferSinkCtx, bufferSink, "out", nullptr, nullptr, filterGraph);

        if (retFilterOut < 0)
        {
            char err[AV_ERROR_MAX_STRING_SIZE];
            av_make_error_string(err, AV_ERROR_MAX_STRING_SIZE, retFilterOut);
            spdlog::error("Failed to create bufferSinkCtx: {}", err);
            r(std::string{"ERROR-CREATE-FILTER-SINK"});
            return;
        }

        enum AVPixelFormat pix_fmts[] = {AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE};
        av_opt_set_int_list(bufferSinkCtx, "pix_fmts", pix_fmts, AV_PIX_FMT_NONE, AV_OPT_SEARCH_CHILDREN);

        // add filters to graph and link them
        const char *filterSpec = "drawtext=text='Legenda Adicionada Automaticamente Via FFMPEG e C++': fontcolor=yellow: bordercolor=black: fontfile='/Users/paulo/Downloads/roboto/Roboto-Black.ttf'";
        const AVFilter *filter = avfilter_get_by_name("drawtext");

        AVFilterInOut *outputs = avfilter_inout_alloc();
        AVFilterInOut *inputs = avfilter_inout_alloc();

        outputs->name = av_strdup("in");
        outputs->filter_ctx = bufferSrcCtx;
        outputs->pad_idx = 0;
        outputs->next = nullptr;
        inputs->name = av_strdup("out");
        inputs->filter_ctx = bufferSinkCtx;
        inputs->pad_idx = 0;
        inputs->next = nullptr;

        if (avfilter_graph_parse_ptr(filterGraph, filterSpec, &inputs, &outputs, nullptr) < 0)
        {
            spdlog::error("Failed to parse filter graph");
            r(std::string{"ERROR-PARSE-FILTER"});
            return;
        }

        if (avfilter_graph_config(filterGraph, nullptr) < 0)
        {
            spdlog::error("Failed to configure filter graph");
            r(std::string{"ERROR-CONFIG-FILTER"});
            return;
        }

        // header
        spdlog::debug("[Mapping :: callbackAddSubtitle] Writing header...");

        if (avformat_write_header(outputFormatCtx, nullptr) < 0)
        {
            spdlog::error("Error writing header");
            r(std::string{"ERROR-WRITE-HEADER"});
            return;
        }

        // read frames and write to output
        AVPacket *packet = av_packet_alloc();
        AVFrame *frame = av_frame_alloc();

        frame->format = inputCodecCtx->pix_fmt;
        frame->width = inputCodecCtx->width;
        frame->height = inputCodecCtx->height;

        AVFrame *filt_frame = av_frame_alloc();

        filt_frame->format = inputCodecCtx->pix_fmt;
        filt_frame->width = inputCodecCtx->width;
        filt_frame->height = inputCodecCtx->height;

        while (av_read_frame(inputFormatCtx, packet) >= 0)
        {
            if (packet->stream_index == videoStreamIndex)
            {
                if (avcodec_send_packet(inputCodecCtx, packet) < 0)
                {
                    spdlog::error("Error sending packet for decoding");
                    r(std::string{"ERROR-SEND-PACKET-DECODE"});
                    return;
                }

                while (avcodec_receive_frame(inputCodecCtx, frame) == 0)
                {
                    // Envia o quadro decodificado para o gráfico de filtro
                    if (av_buffersrc_add_frame_flags(bufferSrcCtx, frame, AV_BUFFERSRC_FLAG_KEEP_REF) < 0)
                    {
                        spdlog::error("Error while feeding the filtergraph");
                        r(std::string{"ERROR-FEED-FILTERGRAPH"});
                        return;
                    }

                    // Recebe um quadro do gráfico de filtro
                    if (av_buffersink_get_frame(bufferSinkCtx, filt_frame) < 0)
                    {
                        spdlog::error("Error while receiving the filtered frame");
                        r(std::string{"ERROR-RECEIVE-FILTERED-FRAME"});
                        return;
                    }

                    // Envia o quadro decodificado para re-codificação
                    int retSendFrame = avcodec_send_frame(outputCodecCtx, filt_frame);
                    if (retSendFrame < 0)
                    {
                        char err[AV_ERROR_MAX_STRING_SIZE];
                        av_make_error_string(err, AV_ERROR_MAX_STRING_SIZE, retSendFrame);
                        spdlog::error("Error sending frame for encoding: {}", err);
                        r(std::string{"ERROR-SEND-FRAME-ENCODE"});
                        return;
                    }

                    AVPacket *output_packet = av_packet_alloc();
                    output_packet->data = nullptr;
                    output_packet->size = 0;

                    // Re-codifica filt_frame para um pacote
                    if (avcodec_receive_packet(outputCodecCtx, output_packet) == 0)
                    {
                        // Escreve o pacote no fluxo de saída
                        av_write_frame(outputFormatCtx, output_packet);
                        av_packet_unref(output_packet);
                    }

                    av_frame_unref(filt_frame);
                }

                // time
                packet->pts = av_rescale_q_rnd(packet->pts, inputFormatCtx->streams[videoStreamIndex]->time_base, outputFormatCtx->streams[videoStreamIndex]->time_base, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
                packet->dts = av_rescale_q_rnd(packet->dts, inputFormatCtx->streams[videoStreamIndex]->time_base, outputFormatCtx->streams[videoStreamIndex]->time_base, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
                packet->duration = av_rescale_q(packet->duration, inputFormatCtx->streams[videoStreamIndex]->time_base, outputFormatCtx->streams[videoStreamIndex]->time_base);
                packet->stream_index = videoStreamIndex;

                // write packet to output video stream
                av_interleaved_write_frame(outputFormatCtx, packet);
            }
            else if (packet->stream_index == audioStreamIndex)
            {
                // rescale timestamps
                packet->pts = av_rescale_q_rnd(packet->pts, inputFormatCtx->streams[audioStreamIndex]->time_base, outputFormatCtx->streams[audioStreamIndex]->time_base, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
                packet->dts = av_rescale_q_rnd(packet->dts, inputFormatCtx->streams[audioStreamIndex]->time_base, outputFormatCtx->streams[audioStreamIndex]->time_base, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
                packet->duration = av_rescale_q(packet->duration, inputFormatCtx->streams[audioStreamIndex]->time_base, outputFormatCtx->streams[audioStreamIndex]->time_base);
                packet->stream_index = audioStreamIndex;

                // write packet to output audio stream
                av_interleaved_write_frame(outputFormatCtx, packet);
            }

            av_packet_unref(packet);
        }

        av_packet_free(&packet);
        av_frame_free(&frame);
        av_frame_free(&filt_frame);

        spdlog::debug("[Mapping :: callbackAddSubtitle] Writing trailer...");

        if (av_write_trailer(outputFormatCtx) < 0)
        {
            spdlog::error("Error writing trailer");
            r(std::string{"ERROR-WRITE-TRAILER"});
            return;
        }

        // cleanup
        spdlog::debug("[Mapping :: callbackAddSubtitle] Cleaning...");

        if (!(outputFormatCtx->oformat->flags & AVFMT_NOFILE))
        {
            avio_closep(&outputFormatCtx->pb);
        }

        avcodec_free_context(&inputCodecCtx);
        avcodec_free_context(&inputAudioCodecCtx);
        avcodec_free_context(&outputCodecCtx);
        avcodec_free_context(&outputAudioCodecCtx);

        avformat_free_context(inputFormatCtx);
        avformat_free_context(outputFormatCtx);

        r(std::string{"OK"});
    }
    catch (const std::exception &e)
    {
        spdlog::error("Error: {}", e.what());
        r(std::string{"ERROR"});
    }
}


  


  The error is :

  


  [2023-10-17 06:30:16.936] [debug] [Mapping :: callbackAddSubtitle] Adding subtitle...
[2023-10-17 06:30:16.936] [debug] [Mapping :: callbackAddSubtitle] Initializing input video...
[NULL @ 0x153604a60] Opening '/Users/paulo/Downloads/movie.mp4' for reading
[file @ 0x6000001fd170] Setting default whitelist 'file,crypto,data'
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x153604a60] Format mov,mp4,m4a,3gp,3g2,mj2 probed with size=2048 and score=100
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x153604a60] ISO: File Type Major Brand: isom
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x153604a60] Unknown dref type 0x206c7275 size 12
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x153604a60] Processing st: 0, edit list 0 - media time: 0, duration: 2669670
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x153604a60] Unknown dref type 0x206c7275 size 12
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x153604a60] Processing st: 1, edit list 0 - media time: 1024, duration: 4272096
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x153604a60] drop a frame at curr_cts: 0 @ 0
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x153604a60] Before avformat_find_stream_info() pos: 113542488 bytes read:110788 seeks:1 nb_streams:2
[h264 @ 0x153604cd0] nal_unit_type: 7(SPS), nal_ref_idc: 3
[h264 @ 0x153604cd0] Decoding VUI
[h264 @ 0x153604cd0] nal_unit_type: 8(PPS), nal_ref_idc: 3
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x153604a60] demuxer injecting skip 1024 / discard 0
[aac @ 0x1536056f0] skip 1024 / discard 0 samples due to side data
[h264 @ 0x153604cd0] nal_unit_type: 7(SPS), nal_ref_idc: 3
[h264 @ 0x153604cd0] Decoding VUI
[h264 @ 0x153604cd0] nal_unit_type: 8(PPS), nal_ref_idc: 3
[h264 @ 0x153604cd0] nal_unit_type: 6(SEI), nal_ref_idc: 0
[h264 @ 0x153604cd0] nal_unit_type: 5(IDR), nal_ref_idc: 3
[h264 @ 0x153604cd0] Format yuv420p chosen by get_format().
[h264 @ 0x153604cd0] Reinit context to 1088x1920, pix_fmt: yuv420p
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x153604a60] All info found
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x153604a60] After avformat_find_stream_info() pos: 195211 bytes read:305951 seeks:2 frames:2
[2023-10-17 06:30:18.160] [debug] [Mapping :: callbackAddSubtitle] Initializing input audio...
[h264 @ 0x143604330] nal_unit_type: 7(SPS), nal_ref_idc: 3
[h264 @ 0x143604330] Decoding VUI
[h264 @ 0x143604330] nal_unit_type: 8(PPS), nal_ref_idc: 3
[2023-10-17 06:30:18.160] [debug] [Mapping :: callbackAddSubtitle] Initializing output video...
[h264 @ 0x143611ec0] nal_unit_type: 7(SPS), nal_ref_idc: 3
[h264 @ 0x143611ec0] Decoding VUI
[h264 @ 0x143611ec0] nal_unit_type: 8(PPS), nal_ref_idc: 3
[file @ 0x6000001f4000] Setting default whitelist 'file,crypto,data'
[2023-10-17 06:30:18.167] [debug] Pixel Format: YUV420P
[2023-10-17 06:30:18.167] [debug] [Mapping :: callbackAddSubtitle] Initializing output audio...
[2023-10-17 06:30:18.167] [debug] [Mapping :: callbackAddSubtitle] Initializing filters...
[2023-10-17 06:30:18.168] [debug] [Mapping :: callbackAddSubtitle] Buffer src args: video_size=1080x1920:pix_fmt=0:time_base=1/30000:pixel_aspect=1/1
detected 10 logical cores
[in @ 0x6000004ec0b0] Setting 'video_size' to value '1080x1920'
[in @ 0x6000004ec0b0] Setting 'pix_fmt' to value '0'
[in @ 0x6000004ec0b0] Setting 'time_base' to value '1/30000'
[in @ 0x6000004ec0b0] Setting 'pixel_aspect' to value '1/1'
[in @ 0x6000004ec0b0] w:1080 h:1920 pixfmt:yuv420p tb:1/30000 fr:0/1 sar:1/1
[AVFilterGraph @ 0x6000017e8000] Setting 'text' to value 'Legenda Adicionada Automaticamente Via FFMPEG e C++'
[AVFilterGraph @ 0x6000017e8000] Setting 'fontcolor' to value 'yellow'
[AVFilterGraph @ 0x6000017e8000] Setting 'bordercolor' to value 'black'
[AVFilterGraph @ 0x6000017e8000] Setting 'fontfile' to value '/Users/paulo/Downloads/roboto/Roboto-Black.ttf'
[AVFilterGraph @ 0x6000017e8000] query_formats: 3 queried, 2 merged, 0 already done, 0 delayed
[2023-10-17 06:30:18.172] [debug] [Mapping :: callbackAddSubtitle] Writing header...
[h264 @ 0x143604330] nal_unit_type: 6(SEI), nal_ref_idc: 0
[h264 @ 0x143604330] nal_unit_type: 5(IDR), nal_ref_idc: 3
[h264 @ 0x143604330] Format yuv420p chosen by get_format().
[h264 @ 0x143604330] Reinit context to 1088x1920, pix_fmt: yuv420p
[Parsed_drawtext_0 @ 0x6000004f4160] Copying data in avfilter.
[Parsed_drawtext_0 @ 0x6000004f4160] n:0 t:0.000000 text_w:424 text_h:16 x:0 y:0
[2023-10-17 06:30:18.182] [error] Error sending frame for encoding: Invalid argument
Returned Value: ERROR-SEND-FRAME-ENCODE


  


• Cohort Analysis 101 : How-To, Examples & Top Tools

  13 novembre 2023, par Erin — Analytics Tips

  Imagine that a farmer is trying to figure out why certain hens are laying large brown eggs and others are laying average-sized white eggs.

  The farmer decides to group the hens into cohorts based on what kind of eggs they lay to make it easier to detect patterns in their day-to-day lives. After careful observation and analysis, she discovered that the hens laying big brown eggs ate more than the roost’s other hens.

  With this cohort analysis, the farmer deduced that a hen’s body weight directly corresponds to egg size. She can now develop a strategy to increase the body weight of her hens to sell more large brown eggs, which are very popular at the weekly farmers’ market.

  Cohort analysis has a myriad of applications in the world of web analytics. Like our farmer, you can use it to better understand user behaviour and reap the benefits of your efforts. This article will discuss the best practices for conducting an effective cohort analysis and compare the top cohort analysis tools for 2024. 

  What is cohort analysis ?

  By definition, cohort analysis refers to a technique where users are grouped based on shared characteristics or behaviours and then examined over a specified period.

  Think of it as a marketing superpower, enabling you to comprehend user behaviours, craft personalised campaigns and allocate resources wisely, ultimately resulting in improved performance and better ROI.

  Why does cohort analysis matter ?

  In web analytics, a cohort is a group of users who share a certain behaviour or characteristic. The goal of cohort analysis is to uncover patterns and compare the performance and behaviour of different cohorts over time.

  An example of a cohort is a group of users who made their first purchase during the holidays. By analysing this cohort, you could learn more about their behaviour and buying patterns. You may discover that this cohort is more likely to buy specific product categories as holiday gifts — you can then tailor future holiday marketing campaigns to include these categories. 

  Types of cohort analysis

  There are a few different types of notable cohorts : 

  1. Time-based cohorts are groups of users categorised by a specific time. The example of the farmer we went over at the beginning of this section is a great example of a time-based cohort.
  2. Acquisition cohorts are users acquired during a specific time frame, event or marketing channel. Analysing these cohorts can help you determine the value of different acquisition methods. 
  3. Behavioural cohorts consist of users who show similar patterns of behaviour. Examples include frequent purchases with your mobile app or digital content engagement. 
  4. Demographic cohorts share common demographic characteristics like age, gender, education level and income. 
  5. Churn cohorts are buyers who have cancelled a subscription/stopped using your service within a specific time frame. Analysing churn cohorts can help you understand why customers leave.
  6. Geographic cohorts are pretty self-explanatory — you can use them to tailor your marketing efforts to specific regions. 
  7. Customer journey cohorts are based on the buyer lifecycle — from acquisition to adoption to retention. 
  8. Product usage cohorts are buyers who use your product/service specifically (think basic users, power users or occasional users). 

  Best practices for conducting a cohort analysis 

  So, you’ve decided you want to understand your user base better but don’t know how to go about it. Perhaps you want to reduce churn and create a more engaging user experience. In this section, we’ll walk you through the dos and don’ts of conducting an effective cohort analysis. Remember that you should tailor your cohort analysis strategy for organisation-specific goals.

  

  1. Preparing for cohort analysis : 

  • • First, define specific goals you want your cohort analysis to achieve. Examples include improving conversion rates or reducing churn.
    • Choosing the right time frame will help you compare short-term vs. long-term data trends. 

  2. Creating effective cohorts : 

  • • Define your segmentation criteria — anything from demographics to location, purchase history or user engagement level. Narrowing in on your specific segments will make your cohort analysis more precise. 
    • It’s important to find a balance between cohort size and similarity. If your cohort is too small and diverse, you won’t be able to find specific behavioural patterns.

  3. Performing cohort analysis :

  • • • Study retention rates across cohorts to identify patterns in user behaviour and engagement over time. Pay special attention to cohorts with high retention or churn rates. 
      • Analysing cohorts can reveal interesting behavioural insights — how do specific cohorts interact with your website ? Do they have certain preferences ? Why ? 

  4. Visualising and interpreting data :

  • • Visualising your findings can be a great way to reveal patterns. Line charts can help you spot trends, while bar charts can help you compare cohorts.
    • Guide your analytics team on how to interpret patterns in cohort data. Watch for sudden drops or spikes and what they could mean. 

  5. Continue improving :

  • • User behaviour is constantly evolving, so be adaptable. Continuous tracking of user behaviour will help keep your strategies up to date. 
    • Encourage iterative analysis optimisation based on your findings. 

  

  The top cohort analysis tools for 2024

  In this section, we’ll go over the best cohort analysis tools for 2024, including their key features, cohort analysis dashboards, cost and pros and cons.

  1. Matomo

  

  Matomo is an open-source, GDPR-compliant web analytics solution that offers cohort analysis as a standard feature in Matomo Cloud and is available as a plugin for Matomo On-Premise. Pairing traditional web analytics with cohort analysis will help you gain even deeper insights into understanding user behaviour over time. 

  You can use the data you get from web analytics to identify patterns in user behaviour and target your marketing strategies to specific cohorts. 

  Key features

  • Matomo offers a cohorts table that lets you compare cohorts side-by-side, and it comes with a time series.
    • All core session and conversion metrics are also available in the Cohorts report.
  • Create custom segments based on demographics, geography, referral sources, acquisition date, device types or user behaviour. 
  • Matomo provides retention analysis so you can track how many users from a specific cohort return to your website and when. 
  • Flexibly analyse your cohorts with custom reports. Customise your reports by combining metrics and dimensions specific to different cohorts. 
  • Create cohorts based on events or interactions with your website. 
  • Intuitive, colour-coded data visualisation, so you can easily spot patterns.

  Pros

  • No setup is needed if you use the JavaScript tracker
  • You can fetch cohort without any limit
  • 100% accurate data, no AI or Machine Learning data filling, and without the use of data sampling

  Cons

  • Matomo On-Premise (self-hosted) is free, but advanced features come with additional charges
  • Servers and technical know-how are required for Matomo On-Premise. Alternatively, for those not ready for self-hosting, Matomo Cloud presents a more accessible option and starts at $19 per month.

  Price : 

  • Matomo Cloud : 21-day free trial, then starts at $19 per month (includes Cohorts).
  • Matomo On-Premise : Free to self-host ; Cohorts plugin : 30-day free trial, then $99 per year.

  2. Mixpanel

  

  Mixpanel is a product analytics tool designed to help teams better understand user behaviour. It is especially well-suited for analysing user behaviour on iOS and Android apps. It offers various cohort analytics features that can be used to identify patterns and engage your users. 

  Key features

  • Create cohorts based on criteria such as sign-up date, first purchase date, referral source, geographic location, device type or another custom event/property. 
  • Compare how different cohorts engage with your app with Mixpanel’s comparative analysis features.
  • Create interactive dashboards, charts and graphs to visualise data.
  • Mixpanel provides retention analysis tools to see how often users return to your product over time. 
  • Send targeted messages and notifications to specific cohorts to encourage user engagement, announce new features, etc. 
  • Track and analyse user behaviours within cohorts — understand how different types of users engage with your product.

  Pros

  • Easily export cohort analysis data for further analysis
  • Combined with Mixpanel reports, cohorts can be a powerful tool for improving your product

  Cons

  • With the free Mixpanel plan, you can’t save cohorts for future use
  • Enterprise-level pricing is expensive
  • Time-consuming cohort creation process

  Price : Free basic version. The growth version starts at £16/month.

  3. Amplitude

  

  Amplitude is another product analytics solution that can help businesses track user interactions across digital platforms. Amplitude offers a standard toolkit for in-depth cohort analysis.

  Key features

  • Create cohorts based on criteria such as sign-up date, first purchase date, referral source, geographic location, device type or another custom event/property. 
  • Conduct behavioural, time-based and retention analyses.
  • Create custom reports with custom data.
  • Segment cohorts further based on additional criteria and compare multiple cohorts side-by-side.

  Pros

  • Highly customisable and flexible
  • Quick and simple setup

  Cons

  • Steep learning curve — requires significant training 
  • Slow loading speed
  • High price point compared to other tools

  Price : Free basic version. Plus version starts at £40/month (billed annually).

  4. Kissmetrics

  

  Kissmetrics is a customer engagement automation platform that offers powerful analytics features. Kissmetrics provides behavioural analytics, segmentation and email campaign automation. 

  Key features

  • Create cohorts based on demographics, user behaviour, referral sources, events and specific time frames.
  • The user path tool provides path visualisation so you can identify common paths users take and spot abandonment points. 
  • Create and optimise conversion funnels.
  • Customise events, user properties, funnels, segments, cohorts and more.

  Pros

  • Powerful data visualisation options
  • Highly customisable

  Cons

  • Difficult to install
  • Not well-suited for small businesses
  • Limited integration with other tools

  Price : Starting at £21/month for 10k events (billed monthly).

  Improve your cohort analysis with Matomo

  When choosing a cohort analysis tool, consider factors such as the tool’s ease of integration with your existing systems, data accuracy, the flexibility it offers in defining cohorts, the comprehensiveness of reporting features, and its scalability to accommodate the growth of your data and analysis needs over time. Moreover, it’s essential to confirm GDPR compliance to uphold rigorous privacy standards. 

  If you’re ready to understand your user’s behaviour, take Matomo for a test drive. Paired with web analytics, this powerful combination can advance your marketing efforts. Start your 21-day free trial today — no credit card required.

• What is a Cohort Report ? A Beginner’s Guide to Cohort Analysis

  3 janvier 2024, par Erin

  Handling your user data as a single mass of numbers is rarely conducive to figuring out meaningful patterns you can use to improve your marketing campaigns.

  A cohort report (or cohort analysis) can help you quickly break down that larger audience into sequential segments and contrast and compare based on various metrics. As such, it is a great tool for unlocking more granular trends and insights — for example, identifying patterns in engagement and conversions based on the date users first interacted with your site.

  In this guide, we explain the basics of the cohort report and the best way to set one up to get the most out of it.

  What is a cohort report ?

  In a cohort report, you divide a data set into groups based on certain criteria — typically a time-based cohort metric like first purchase date — and then analyse the data across those segments, looking for patterns.

  Date-based cohort analysis is the most common approach, often creating cohorts based on the day a user completed a particular action — signed up, purchased something or visited your website. Depending on the metric you choose to measure (like return visits), the cohort report might look something like this :

  

  Note that this is not a universal benchmark or anything of the sort. The above is a theoretical cohort analysis based on app users who downloaded the app, tracking and comparing the retention rates as the days go by. 

  The benchmarks will be drastically different depending on the metric you’re measuring and the basis for your cohorts. For example, if you’re measuring returning visitor rates among first-time visitors to your website, expect single-digit percentages even on the second day.

  Your industry will also greatly affect what you consider positive in a cohort report. For example, if you’re a subscription SaaS, you’d expect high continued usage rates over the first week. If you sell office supplies to companies, much less so.

  What is an example of a cohort ?

  As we just mentioned, a typical cohort analysis separates users or customers by the date they first interacted with your business — in this case, they downloaded your app. Within that larger analysis, the users who downloaded it on May 3 represent a single cohort.

  

  In this case, we’ve chosen behaviour and time — the app download day — to separate the user base into cohorts. That means every specific day denotes a specific cohort within the analysis.

  Diving deeper into an individual cohort may be a good idea for important holidays or promotional events like Black Friday.

  Of course, cohorts don’t have to be based on specific behaviour within certain periods. You can also create cohorts based on other dimensions :

  • Transactional data — revenue per user
  • Churn data — date of churn
  • Behavioural cohort — based on actions taken on your website, app or e-commerce store, like the number of sessions per user or specific product pages visited
  • Acquisition cohort — which channel referred the user or customer

  For more information on different cohort types, read our in-depth guide on cohort analysis.

  How to create a cohort report (and make sense of it)

  Matomo makes it easy to view and analyse different cohorts (without the privacy and legal implications of using Google Analytics).

  Here are a few different ways to set up a cohort report in Matomo, starting with our built-in cohorts report.

  Cohort reports

  With Matomo, cohort reports are automatically compiled based on the first visit date. The default metric is the percentage of returning visitors.

  

  Changing the settings allows you to create multiple variations of cohort analysis reports.

  Break down cohorts by different metrics

  The percentage of returning visits can be valuable if you’re trying to improve early engagement in a SaaS app onboarding process. But it’s far from your only option.

  You can also compare performance by conversion, revenue, bounce rate, actions per visit, average session duration or other metrics.

  

  Change the time and scope of your cohort analysis

  Splitting up cohorts by single days may be useless if you don’t have a high volume of users or visitors. If the average cohort size is only a few users, you won’t be able to identify reliable patterns. 

  Matomo lets you set any time period to create your cohort analysis report. Instead of the most recent days, you can create cohorts by week, month, year or custom date ranges. 

  

  Cohort sizes will depend on your customer base. Make sure each cohort is large enough to encapsulate all the customers in that cohort and not so small that you have insignificant cohorts of only a few customers. Choose a date range that gives you that without scaling it too far so you can’t identify any seasonal trends.

  Cohort analysis can be a great tool if you’ve recently changed your marketing, product offering or onboarding. Set the data range to weekly and look for any impact in conversions and revenue after the changes.

  Using the “compare to” feature, you can also do month-over-month, quarter-over-quarter or any custom date range comparisons. This approach can help you get a rough overview of your campaign’s long-term progress without doing any in-depth analysis.

  You can also use the same approach to compare different holiday seasons against each other.

  If you want to combine time cohorts with segmentation, you can run cohort reports for different subsets of visitors instead of all visitors. This can lead to actionable insights like adjusting weekend or specific seasonal promotions to improve conversion rates.

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  Easily create custom cohort reports beyond the time dimension

  If you want to split your audience into cohorts by focusing on something other than time, you will need to create a custom report and choose another dimension. In Matomo, you can choose from a wide range of cohort metrics, including referrers, e-commerce signals like viewed product or product category, form submissions and more.

  

  Then, you can create a simple table-based report with all the insights you need by choosing the metrics you want to see. For example, you could choose average visit duration, bounce rate and other usage metrics.

  

  If you want more revenue-focused insights, add metrics like conversions, add-to-cart and other e-commerce events.

  Custom reports make it easy to create cohort reports for almost any dimension. You can use any metric within demographic and behavioural analytics to create a cohort. (You can explore the complete list of our possible segmentation metrics.)

  We cover different types of custom reports (and ideas for specific marketing campaigns) in our guide on custom segmentation.

  Create your first cohort report and gain better insights into your visitors

  Cohort reports can help you identify trends and the impact of short-term marketing efforts like events and promotions.

  With Matomo cohort reports you have the power to create complex custom reports for various cohorts and segments. 

  If you’re looking for a powerful, easy-to-use web analytics solution that gives you 100% accurate data without compromising your users’ privacy, Matomo is a great fit. Get started with a 21-day free trial today. No credit card required. 

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