Recherche avancée

Sur d’autres sites (11072)

• How to covert video and extract frame from video using FFMPEG in single command

  13 juillet 2013, par kheya

  I am trying to convert and extract image frame from a video file in single command
  I can do this in 2 steps but I want to use pipe like technique to do this

  This is what I have :
  for %%a in ("*.avi") do ffmpeg -i "%%a" -c:v libx264 -preset slow -crf 20 -c:a libvo_aacenc -b:a 128k "%%~na.mp4" <— converts correctly

  I need to incorporate this extract command :

  ffmpeg -i inputfile.avi  -r  1  -t  4  image-%d.jpeg

  Merging two commands giving error.

  How do I do it ?

  EDIT :
  This is what I have. But it just converts the video, no jpg image created as second output

  for %%a in ("*.avi") do ffmpeg -i "%%a" -c:v libx264 -preset slow -crf 20 -c:a libvo_aacenc -b:a 128k "%%~na.mp4" | ffmpeg -r 1 -s 4cif "%%~na.jpeg"

• Re-encode a video keeping the GOP structure of the original video [closed]

  5 avril, par Baltar27

  Is there a way to re-encode a video with ffmpeg keeping the GOP structure of the original file ? That is, if a frame is IDR, I, B or P in the input file, keep the same type in the output file, even if the GOP is variable and/or adaptive (it changes dynamically GOP type Open/Closed, the I period N or the P period M). Encoding in this way allows to maintain the maximum quality as the Open/Closed, I/B/P and GOP length decisions has been taken already by the original encoder.

  &#xA;

• FFMPEG C++ API audio/video sync, video is longer [closed]

  11 mai 2023, par Gábor Gombor

  I create a video from frames in C++ with a given FPS and supply it to FFMPEG API. I record from an Unreal engine viewport and feed FFMPEG with the images. In this interval I have also an audio track in FLAC which I want sync with the video. When the music ends, I close the video and merge them, but the final video has sync problems, the video is a little bit longer than the audio, so I will have an increasing delay. For example I record 0:55 secs, the audio is ok=same length, but the video from frames will be 0:56 secs.

  &#xA;

  I think the following code is problematic :

  &#xA;

  bool MyVideoExporter::writeFrame(OutputStream* oStream, AVFrame* frame, int& framePTS)
{
    auto* packet = oStream->pkt->pkt;
    auto* codecContext = oStream->enc->codecContext;

    frame->pts = framePTS;
    frame->pkt_dts = frame->pts;

    auto ret = avcodec_send_frame(codecContext, frame);
    if (ret >= 0) {
        auto retVal = 0;
        while (retVal >= 0) {
            retVal = avcodec_receive_packet(codecContext, packet);
            if (retVal == AVERROR(EAGAIN) || retVal == AVERROR_EOF) break;
            else if (retVal < 0) {
                return false;
            }

            // rescale to audio, usually 1/44100
            av_packet_rescale_ts(packet, m_audiotimestamp, oStream->st->time_base);
            // rescale to FPS, usually 1/30 or 1/60
            av_packet_rescale_ts(packet, codecContext->time_base, oStream->st->time_base);

            packet->stream_index = oStream->st->index;

            retVal = av_interleaved_write_frame(m_avFormatContext.avFormatContext, packet);
            if (retVal < 0) {
                return false;
            }

            framePTS++;
        }

        return retVal == AVERROR_EOF;
    }

    return false;
}



  &#xA;

  Any idea what is wrong ?

  &#xA;

  I tried change the order of av_packet_rescale_ts lines or move the frame increase code to another places, but getting far worse results.

  &#xA;