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• Libav FFv1 read_quant_table decoding errors

  16 November 2023, by flansel

  I am having trouble encoding and decoding video using the 'ffv1' codec. Interestingly when the width and height are 640 or less, this works correctly, but with any "large" frame size such as 1280x720 I get the follow errors ...

  


  [ffv1 @ 0x5612f4ab2240] read_quant_table error
[ffv1 @ 0x5612f4ab2240] Cannot decode non-keyframe without valid keyframe


  


  Are there any options which need to be set, or am I doing something else incorrectly, I made the example very minimal, I am aware that I am not writing an image to the frame and simply allocating garbage in the buffers among other things.
Thanks in advance.

  


  // minimal example
// ...
#define FRAMES (500)

int main(int argc, char **argv)
{
    AVCodecContext *enc, *dec;
    AVFrame *frame = av_frame_alloc();
    AVFrame *decoded_frame = av_frame_alloc();
    AVPacket *packet = av_packet_alloc();
    AVPacket *padded_packet = av_packet_alloc();

    const AVCodec *enc_codec = avcodec_find_encoder_by_name("ffv1");
    const AVCodec *dec_codec = avcodec_find_decoder_by_name("ffv1");
    enc = avcodec_alloc_context3(enc_codec);
    dec = avcodec_alloc_context3(dec_codec);

    enc->width   = 1280;
    enc->height  = 720;
    enc->pix_fmt = AV_PIX_FMT_YUV420P;
    enc->time_base.num = 1001;
    enc->time_base.den = 60000;

    dec->width  = enc->width;
    dec->height = enc->height;

    avcodec_open2(enc, enc_codec, NULL);
    avcodec_open2(dec, dec_codec, NULL);

    frame->height = enc->height;
    frame->width  = enc->width;
    frame->format = enc->pix_fmt;
    av_frame_get_buffer(frame, 32);
    printf("frame linesz %i,%i,%i\n", frame->linesize[0], frame->linesize[1], frame->linesize[2]);

    for (int i = 0; i < FRAMES; ++i)
    {
        avcodec_send_frame(enc, frame);
        while (!avcodec_receive_packet(enc, packet))
        {
            av_new_packet(padded_packet, packet->size + AV_INPUT_BUFFER_PADDING_SIZE);
            padded_packet->size -= AV_INPUT_BUFFER_PADDING_SIZE;

            memset(padded_packet->data, 0, padded_packet->size);
            memcpy(padded_packet->data, packet->data, packet->size);
            printf("frame %i encoded %i bytes\n", i, padded_packet->size);
            if (!avcodec_send_packet(dec, padded_packet))
            {
                printf("sent bytes to decoder\n");
            }
        }

        while (!avcodec_receive_frame(dec, decoded_frame))
        {
            printf("decoded frame height %i, width %i\n", decoded_frame->height, decoded_frame->width);
        }
        usleep(16000);
    }
    return 0;
}


  


• Allocate AVFrame for sws_scale()

  13 March 2020, by Slav

  Trying to write program which uses libav to extract raw pixel data ( BMP) from arbitrary video. Everything goes well except sws_scale() failing to convert AVFrame to RGB24.

  I formulated minimal example of it where AVFrame is being created and initialized with 4 different methods found on internet: https://github.com/SlavMFM/libav_bmp_example - all of them fail in different ways. How can I fix it so sws_scale() does the convertion?

• Raspberry Pi and FFMpeg live streaming video to backend Node.js server, but how do I deliver it to the front end?

  2 August 2023, by qwet142

  I'm attempting this setup to live stream video from a Raspberry Pi to a publicly available website, and from the backend server using Node.js and Express, I would like to serve it to the front end with minimal latency available to many viewers (will be hosted somewhere like Netlify to handle distribution).

  


  WebRTC is too complex for my use case and timeframe. HLC appears to have too high a latency as I need <4s consistently. I would like to something compatible with Node.js. I am a beginner in this domain, familiar only with general programming and web development.

  &#xA;