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Sur d’autres sites (5651)

  • 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.

    


    I think the following code is problematic :

    


    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;
}



    


    Any idea what is wrong ?

    


    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.

    


  • FFMPEG merging audio and video to get resulting video

    26 septembre 2016, par King

    I need to merge audio and video using ffmpeg so that, it should result in a video with the same duration as of audio.

    I have tried 2 commands for that requirement in my linux terminal. Both the commands work for a few of the input videos ; but for some other input_videos, they produce output same as the input video, the audio doesn’t get merged.

    The commands, I have tried are -

    ffmpeg -i wonders.mp4 -i Carefull.mp3 -c copy testvid.mp4

    and

    ffmpeg -i wonders.mp4 -i Carefull.mp3 -strict -2 testvid.mp4

    and

    ffmpeg -i video.mp4 -i audio.wav -c:v copy -c:a aac -strict
    experimental output.mp4

    and these are my input videos -

    1. samplevid.mp4

    https://vid.me/z44E

    duration - 28 seconds

    size - 1.1 MB

    status - working

    And

    1. wonders.mp4

    https://vid.me/gyyB

    duration - 97 seconds

    size - 96 MB

    status - not working

    I have observed that the large size (more than 2MB) of the input video is probably the issue.

    But, still I want the fix.

  • how to check the number of duplicated frame for video 1sec ( about 30frames ) from video start and want to apply this for mpdecimate

    20 octobre 2018, par cool jobs

    How to check the number of duplicated frame for video 1sec ( about 30frames ) from video beginning point ? I want to apply this for mpdecimate with audio. Some videos have three duplicated frames, some videos - 15 duplicated frame, some videos have 19 duplicated frames.. so it looks I need a variable or math operator in ffmpeg as expression.

    1. some video have duplicated frames at beginning point , but it is
      not same always the number of duplicated frames.
    2. if get back variable which is for the number of duplicated frames
      from step-1 then split and trim apply mpdecimate with audio as
      much as step-1 variable returned, finally do concatenate each other.

    Is this possible with -filter_complex for one line ffmpeg command ?