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• Adding text to movie using ffmpeg

  23 août 2014, par microspace

  I use git to track *.ass subtitle files.
  Here is example of *.ass file :

  [Script Info]
  
  ; Script generated by Aegisub 3.1.2
  
  ; http://www.aegisub.org/
  
  Title: Default Aegisub file
  
  ScriptType: v4.00+
  
  
  
  [V4+ Styles]
  
  Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour,    BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
  
  Style: Default,Arial,20,&H00FFFFFF,&H000000FF,&H00000000,&H00000000,0,0,0,0,100,100,0,0,1,2,2,2,10,10,10,1
  
  Style: titr,DejaVu     
  
  
  
  Sans,20,&H007DDBFA,&H000000FF,&H00000000,&HFF000000,0,0,0,0,100,100,0,0,1,2,2,1,10,10,10,1
  
  
  
  [Events]
  
  Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
  
  Dialogue: 0,0:00:00.46,0:00:11.22,Default,,0,0,0,,Если это можно было бы
  
  Dialogue: 0,0:00:03.44,0:00:08.96,titr,,0,0,0,,{\pos(20,240)\fad(600,600)}бывший министр

  After commit I burn subtitles into video :

  ffmpeg -i video.avi -vf "ass=subtitle.ass" out.avi

  My goal is to show commit date for 10 second at the start of movie. This should be done automatically.

  1) It can be easily done with by modifying subtitle.ass itself, but I can’t do it after commit and there are other reasons.

  2) It can be done by ffmpeg from command line : How to use ffmpeg to add a text to avi video ?

  Problem is that in this case text will be shown for the whole lenght of movie.

  3) I can copy *.ass file to temporary directory, insert date, render and delete *.ass file.

  Is there a simpler way ?

• How can I automatically embed commit information into a subtitles file that I'm tracking ?

  23 février 2015, par microspace

  I use git to track *.ass subtitle files.
  Here is example of *.ass file :

  [Script Info]
  
  ; Script generated by Aegisub 3.1.2
  
  ; http://www.aegisub.org/
  
  Title: Default Aegisub file
  
  ScriptType: v4.00+
  
  
  
  [V4+ Styles]
  
  Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour,    BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
  
  Style: Default,Arial,20,&H00FFFFFF,&H000000FF,&H00000000,&H00000000,0,0,0,0,100,100,0,0,1,2,2,2,10,10,10,1
  
  Style: titr,DejaVu     
  
  
  
  Sans,20,&H007DDBFA,&H000000FF,&H00000000,&HFF000000,0,0,0,0,100,100,0,0,1,2,2,1,10,10,10,1
  
  
  
  [Events]
  
  Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
  
  Dialogue: 0,0:00:00.46,0:00:11.22,Default,,0,0,0,,Если это можно было бы
  
  Dialogue: 0,0:00:03.44,0:00:08.96,titr,,0,0,0,,{\pos(20,240)\fad(600,600)}бывший министр

  After commit I burn subtitles into video :

  ffmpeg -i video.avi -vf "ass=subtitle.ass" out.avi

  My goal is to show commit date for 10 second at the start of movie. This should be done automatically.

  1) It can be easily done with by modifying subtitle.ass itself, but I can’t do it after commit and there are other reasons.

  2) It can be done by ffmpeg from command line : How to use ffmpeg to add a text to avi video ?

  Problem is that in this case text will be shown for the whole lenght of movie.

  3) I can copy *.ass file to temporary directory, insert date, render and delete *.ass file.

  Is there a simpler way ?

• Decode mp3 using FFMpeg, Android NDK - What is wrong with my AVFormatContext ?

  27 février 2020, par michpohl

  I am trying to decode am MP3 file to a raw PCM stream using FFMpeg via JNI on Android. I have compiled the latest FFMpeg version (4.2) and added it to my app. This did not make any problems.
  The goal is to be able to use mp3 files from the device’s storage for playback with oboe

  Since I am relatively inexperienced with both C++ and FFMpeg, my approach is based upon this :
  oboe’s RhythmGame example

  I have based my FFMpegExtractorclass on the one found in the example here. With the help of StackOverflow the AAssetManageruse was removed and instead a MediaSource helper class now serves as a wrapper for my stream (see here)

  But unfortunately, creating the AVFormatContext doesn’t work right - and I can’t seem to understand why. Since I have very limited understanding of correct pointer usage and C++ memory management, I suspect it’s most likely I’m doing something wrong in that area. But honestly, I have no idea.

  This is my FFMpegExtractor.h :

  #define MYAPP_FFMPEGEXTRACTOR_H
  
  
  
  extern "C" {
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libswresample></libswresample>swresample.h>
  
  #include <libavutil></libavutil>opt.h>
  
  }
  
  
  
  #include <cstdint>
  
  #include <android></android>asset_manager.h>
  
  #include 
  
  #include <fstream>
  
  #include "MediaSource.cpp"
  
  
  
  
  
  class FFMpegExtractor {
  
  public:
  
  
  
      FFMpegExtractor();
  
  
  
      ~FFMpegExtractor();
  
  
  
      int64_t decode2(char *filepath, uint8_t *targetData, AudioProperties targetProperties);
  
  
  
  private:
  
      MediaSource *mSource;
  
  
  
      bool createAVFormatContext(AVIOContext *avioContext, AVFormatContext **avFormatContext);
  
  
  
      bool openAVFormatContext(AVFormatContext *avFormatContext);
  
  
  
      int32_t cleanup(AVIOContext *avioContext, AVFormatContext *avFormatContext);
  
  
  
      bool getStreamInfo(AVFormatContext *avFormatContext);
  
  
  
      AVStream *getBestAudioStream(AVFormatContext *avFormatContext);
  
  
  
      AVCodec *findCodec(AVCodecID id);
  
  
  
      void printCodecParameters(AVCodecParameters *params);
  
  
  
      bool createAVIOContext2(const std::string &amp;filePath, uint8_t *buffer, uint32_t bufferSize,
  
                              AVIOContext **avioContext);
  
  };
  
  
  
  
  
  #endif //MYAPP_FFMPEGEXTRACTOR_H
  
  </fstream></cstdint>

  This is FFMPegExtractor.cpp :

  #include <memory>
  
  #include <oboe></oboe>Definitions.h>
  
  #include "FFMpegExtractor.h"
  
  #include "logging.h"
  
  #include <fstream>
  
  
  
  FFMpegExtractor::FFMpegExtractor() {
  
      mSource = new MediaSource;
  
  }
  
  
  
  FFMpegExtractor::~FFMpegExtractor() {
  
      delete mSource;
  
  }
  
  
  
  constexpr int kInternalBufferSize = 1152; // Use MP3 block size. https://wiki.hydrogenaud.io/index.php?title=MP3
  
  
  
  /**
  
   * Reads from an IStream into FFmpeg.
  
   *
  
   * @param ptr       A pointer to the user-defined IO data structure.
  
   * @param buf       A buffer to read into.
  
   * @param buf_size  The size of the buffer buff.
  
   *
  
   * @return The number of bytes read into the buffer.
  
   */
  
  
  
  
  
  // If FFmpeg needs to read the file, it will call this function.
  
  // We need to fill the buffer with file's data.
  
  int read(void *opaque, uint8_t *buffer, int buf_size) {
  
      MediaSource *source = (MediaSource *) opaque;
  
      return source->read(buffer, buf_size);
  
  }
  
  
  
  // If FFmpeg needs to seek in the file, it will call this function.
  
  // We need to change the read pos.
  
  int64_t seek(void *opaque, int64_t offset, int whence) {
  
      MediaSource *source = (MediaSource *) opaque;
  
      return source->seek(offset, whence);
  
  }
  
  
  
  
  
  // Create and save a MediaSource instance.
  
  bool FFMpegExtractor::createAVIOContext2(const std::string &amp;filepath, uint8_t *buffer, uint32_t bufferSize,
  
                                           AVIOContext **avioContext) {
  
  
  
      mSource = new MediaSource;
  
      mSource->open(filepath);
  
      constexpr int isBufferWriteable = 0;
  
  
  
      *avioContext = avio_alloc_context(
  
              buffer, // internal buffer for FFmpeg to use
  
              bufferSize, // For optimal decoding speed this should be the protocol block size
  
              isBufferWriteable,
  
              mSource, // Will be passed to our callback functions as a (void *)
  
              read, // Read callback function
  
              nullptr, // Write callback function (not used)
  
              seek); // Seek callback function
  
  
  
      if (*avioContext == nullptr) {
  
          LOGE("Failed to create AVIO context");
  
          return false;
  
      } else {
  
          return true;
  
      }
  
  }
  
  
  
  bool
  
  FFMpegExtractor::createAVFormatContext(AVIOContext *avioContext,
  
                                         AVFormatContext **avFormatContext) {
  
  
  
      *avFormatContext = avformat_alloc_context();
  
      (*avFormatContext)->pb = avioContext;
  
  
  
      if (*avFormatContext == nullptr) {
  
          LOGE("Failed to create AVFormatContext");
  
          return false;
  
      } else {
  
          LOGD("Successfully created AVFormatContext");
  
          return true;
  
      }
  
  }
  
  
  
  bool FFMpegExtractor::openAVFormatContext(AVFormatContext *avFormatContext) {
  
  
  
      int result = avformat_open_input(&amp;avFormatContext,
  
                                       "", /* URL is left empty because we're providing our own I/O */
  
                                       nullptr /* AVInputFormat *fmt */,
  
                                       nullptr /* AVDictionary **options */
  
      );
  
  
  
      if (result == 0) {
  
          return true;
  
      } else {
  
          LOGE("Failed to open file. Error code %s", av_err2str(result));
  
          return false;
  
      }
  
  }
  
  
  
  bool FFMpegExtractor::getStreamInfo(AVFormatContext *avFormatContext) {
  
  
  
      int result = avformat_find_stream_info(avFormatContext, nullptr);
  
      if (result == 0) {
  
          return true;
  
      } else {
  
          LOGE("Failed to find stream info. Error code %s", av_err2str(result));
  
          return false;
  
      }
  
  }
  
  
  
  AVStream *FFMpegExtractor::getBestAudioStream(AVFormatContext *avFormatContext) {
  
  
  
      int streamIndex = av_find_best_stream(avFormatContext, AVMEDIA_TYPE_AUDIO, -1, -1, nullptr, 0);
  
  
  
      if (streamIndex &lt; 0) {
  
          LOGE("Could not find stream");
  
          return nullptr;
  
      } else {
  
          return avFormatContext->streams[streamIndex];
  
      }
  
  }
  
  
  
  int64_t FFMpegExtractor::decode2(
  
          char* filepath,
  
          uint8_t *targetData,
  
          AudioProperties targetProperties) {
  
  
  
      LOGD("Decode SETUP");
  
      int returnValue = -1; // -1 indicates error
  
  
  
      // Create a buffer for FFmpeg to use for decoding (freed in the custom deleter below)
  
      auto buffer = reinterpret_cast(av_malloc(kInternalBufferSize));
  
  
  
  
  
      // Create an AVIOContext with a custom deleter
  
      std::unique_ptr ioContext{
  
              nullptr,
  
              [](AVIOContext *c) {
  
                  av_free(c->buffer);
  
                  avio_context_free(&amp;c);
  
              }
  
      };
  
      {
  
          AVIOContext *tmp = nullptr;
  
          if (!createAVIOContext2(filepath, buffer, kInternalBufferSize, &amp;tmp)) {
  
              LOGE("Could not create an AVIOContext");
  
              return returnValue;
  
          }
  
          ioContext.reset(tmp);
  
      }
  
      // Create an AVFormatContext using the avformat_free_context as the deleter function
  
      std::unique_ptr formatContext{
  
              nullptr,
  
              &amp;avformat_free_context
  
      };
  
  
  
      {
  
          AVFormatContext *tmp;
  
          if (!createAVFormatContext(ioContext.get(), &amp;tmp)) return returnValue;
  
          formatContext.reset(tmp);
  
      }
  
      if (!openAVFormatContext(formatContext.get())) return returnValue;
  
      LOGD("172");
  
  
  
      if (!getStreamInfo(formatContext.get())) return returnValue;
  
      LOGD("175");
  
  
  
      // Obtain the best audio stream to decode
  
      AVStream *stream = getBestAudioStream(formatContext.get());
  
      if (stream == nullptr || stream->codecpar == nullptr) {
  
          LOGE("Could not find a suitable audio stream to decode");
  
          return returnValue;
  
      }
  
      LOGD("183");
  
  
  
      printCodecParameters(stream->codecpar);
  
  
  
      // Find the codec to decode this stream
  
      AVCodec *codec = avcodec_find_decoder(stream->codecpar->codec_id);
  
      if (!codec) {
  
          LOGE("Could not find codec with ID: %d", stream->codecpar->codec_id);
  
          return returnValue;
  
      }
  
  
  
      // Create the codec context, specifying the deleter function
  
      std::unique_ptr codecContext{
  
              nullptr,
  
              [](AVCodecContext *c) { avcodec_free_context(&amp;c); }
  
      };
  
      {
  
          AVCodecContext *tmp = avcodec_alloc_context3(codec);
  
          if (!tmp) {
  
              LOGE("Failed to allocate codec context");
  
              return returnValue;
  
          }
  
          codecContext.reset(tmp);
  
      }
  
  
  
      // Copy the codec parameters into the context
  
      if (avcodec_parameters_to_context(codecContext.get(), stream->codecpar) &lt; 0) {
  
          LOGE("Failed to copy codec parameters to codec context");
  
          return returnValue;
  
      }
  
  
  
      // Open the codec
  
      if (avcodec_open2(codecContext.get(), codec, nullptr) &lt; 0) {
  
          LOGE("Could not open codec");
  
          return returnValue;
  
      }
  
  
  
      // prepare resampler
  
      int32_t outChannelLayout = (1 &lt;&lt; targetProperties.channelCount) - 1;
  
      LOGD("Channel layout %d", outChannelLayout);
  
  
  
      SwrContext *swr = swr_alloc();
  
      av_opt_set_int(swr, "in_channel_count", stream->codecpar->channels, 0);
  
      av_opt_set_int(swr, "out_channel_count", targetProperties.channelCount, 0);
  
      av_opt_set_int(swr, "in_channel_layout", stream->codecpar->channel_layout, 0);
  
      av_opt_set_int(swr, "out_channel_layout", outChannelLayout, 0);
  
      av_opt_set_int(swr, "in_sample_rate", stream->codecpar->sample_rate, 0);
  
      av_opt_set_int(swr, "out_sample_rate", targetProperties.sampleRate, 0);
  
      av_opt_set_int(swr, "in_sample_fmt", stream->codecpar->format, 0);
  
      av_opt_set_sample_fmt(swr, "out_sample_fmt", AV_SAMPLE_FMT_FLT, 0);
  
      av_opt_set_int(swr, "force_resampling", 1, 0);
  
  
  
      // Check that resampler has been inited
  
      int result = swr_init(swr);
  
      if (result != 0) {
  
          LOGE("swr_init failed. Error: %s", av_err2str(result));
  
          return returnValue;
  
      };
  
      if (!swr_is_initialized(swr)) {
  
          LOGE("swr_is_initialized is false\n");
  
          return returnValue;
  
      }
  
  
  
      // Prepare to read data
  
      int bytesWritten = 0;
  
      AVPacket avPacket; // Stores compressed audio data
  
      av_init_packet(&amp;avPacket);
  
      AVFrame *decodedFrame = av_frame_alloc(); // Stores raw audio data
  
      int bytesPerSample = av_get_bytes_per_sample((AVSampleFormat) stream->codecpar->format);
  
  
  
      LOGD("Bytes per sample %d", bytesPerSample);
  
  
  
      // While there is more data to read, read it into the avPacket
  
      while (av_read_frame(formatContext.get(), &amp;avPacket) == 0) {
  
  
  
          if (avPacket.stream_index == stream->index) {
  
  
  
              while (avPacket.size > 0) {
  
                  // Pass our compressed data into the codec
  
                  result = avcodec_send_packet(codecContext.get(), &amp;avPacket);
  
                  if (result != 0) {
  
                      LOGE("avcodec_send_packet error: %s", av_err2str(result));
  
                      goto cleanup;
  
                  }
  
  
  
                  // Retrieve our raw data from the codec
  
                  result = avcodec_receive_frame(codecContext.get(), decodedFrame);
  
                  if (result != 0) {
  
                      LOGE("avcodec_receive_frame error: %s", av_err2str(result));
  
                      goto cleanup;
  
                  }
  
  
  
                  // DO RESAMPLING
  
                  auto dst_nb_samples = (int32_t) av_rescale_rnd(
  
                          swr_get_delay(swr, decodedFrame->sample_rate) + decodedFrame->nb_samples,
  
                          targetProperties.sampleRate,
  
                          decodedFrame->sample_rate,
  
                          AV_ROUND_UP);
  
  
  
                  short *buffer1;
  
                  av_samples_alloc(
  
                          (uint8_t **) &amp;buffer1,
  
                          nullptr,
  
                          targetProperties.channelCount,
  
                          dst_nb_samples,
  
                          AV_SAMPLE_FMT_FLT,
  
                          0);
  
                  int frame_count = swr_convert(
  
                          swr,
  
                          (uint8_t **) &amp;buffer1,
  
                          dst_nb_samples,
  
                          (const uint8_t **) decodedFrame->data,
  
                          decodedFrame->nb_samples);
  
  
  
                  int64_t bytesToWrite = frame_count * sizeof(float) * targetProperties.channelCount;
  
                  memcpy(targetData + bytesWritten, buffer1, (size_t) bytesToWrite);
  
                  bytesWritten += bytesToWrite;
  
                  av_freep(&amp;buffer1);
  
  
  
                  avPacket.size = 0;
  
                  avPacket.data = nullptr;
  
              }
  
          }
  
      }
  
  
  
      av_frame_free(&amp;decodedFrame);
  
  
  
      returnValue = bytesWritten;
  
  
  
      cleanup:
  
      return returnValue;
  
  }
  
  
  
  void FFMpegExtractor::printCodecParameters(AVCodecParameters *params) {
  
  
  
      LOGD("Stream properties");
  
      LOGD("Channels: %d", params->channels);
  
      LOGD("Channel layout: %"
  
                   PRId64, params->channel_layout);
  
      LOGD("Sample rate: %d", params->sample_rate);
  
      LOGD("Format: %s", av_get_sample_fmt_name((AVSampleFormat) params->format));
  
      LOGD("Frame size: %d", params->frame_size);
  
  }
  
  </fstream></memory>

  And this is the MediaSource.cpp :

  #ifndef MYAPP_MEDIASOURCE_CPP
  
  #define MYAPP_MEDIASOURCE_CPP
  
  
  
  extern "C" {
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libswresample></libswresample>swresample.h>
  
  #include <libavutil></libavutil>opt.h>
  
  }
  
  
  
  #include <cstdint>
  
  #include <android></android>asset_manager.h>
  
  #include 
  
  #include <fstream>
  
  #include "logging.h"
  
  
  
  // wrapper class for file stream
  
  class MediaSource {
  
  public:
  
  
  
      MediaSource() {
  
      }
  
  
  
      ~MediaSource() {
  
          source.close();
  
      }
  
  
  
      void open(const std::string &amp;filePath) {
  
          const char *x = filePath.c_str();
  
          LOGD("Opened %s", x);
  
          source.open(filePath, std::ios::in | std::ios::binary);
  
      }
  
  
  
      int read(uint8_t *buffer, int buf_size) {
  
          // read data to buffer
  
          source.read((char *) buffer, buf_size);
  
          // return how many bytes were read
  
          return source.gcount();
  
      }
  
  
  
      int64_t seek(int64_t offset, int whence) {
  
          if (whence == AVSEEK_SIZE) {
  
              // FFmpeg needs file size.
  
              int oldPos = source.tellg();
  
              source.seekg(0, std::ios::end);
  
              int64_t length = source.tellg();
  
              // seek to old pos
  
              source.seekg(oldPos);
  
              return length;
  
          } else if (whence == SEEK_SET) {
  
              // set pos to offset
  
              source.seekg(offset);
  
          } else if (whence == SEEK_CUR) {
  
              // add offset to pos
  
              source.seekg(offset, std::ios::cur);
  
          } else {
  
              // do not support other flags, return -1
  
              return -1;
  
          }
  
          // return current pos
  
          return source.tellg();
  
      }
  
  
  
  private:
  
      std::ifstream source;
  
  };
  
  
  
  #endif //MYAPP_MEDIASOURCE_CPP
  
  </fstream></cstdint>

  When the code is executed, I can see that I submit the correct file path, so I assume the resource mp3 is there.
  When this code is executed the app crashes in line 103 of FFMpegExtractor.cpp, at formatContext.reset(tmp);

  This is what Android Studio logs when the app crashes :

  --------- beginning of crash
  
  2020-02-27 14:31:26.341 9852-9945/com.user.myapp A/libc: Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x7fffffff0 in tid 9945 (chaelpohl.loopy), pid 9852 (user.myapp)

  This is the (sadly very short) output I get with ndk-stack :

  ********** Crash dump: **********
  
  Build fingerprint: 'samsung/dreamltexx/dreamlte:9/PPR1.180610.011/G950FXXU6DSK9:user/release-keys'
  
  #00 0x0000000000016c50 /data/app/com.user.myapp-D7dBCgHF-vdQNNSald4lWA==/lib/arm64/libavformat.so (avformat_free_context+260)
  
                                                                                                           avformat_free_context
  
                                                                                                           ??:0:0
  
  Crash dump is completed

  I tested a bit around, and every call to my formatContext crashes the app. So I assume there is something wrong with the input I provide to build it but I have no clue how to debug this.

  Any help is appreciated ! (Happy to provide additional resources if something crucial is missing).