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• FFmpeg - Channel relabelling of multi audio tracked video file [closed]

  8 avril 2024, par Mahi s

  I'm trying to relabel the audio channels of the multitrack audio, video files. For some reason I could not relabel the audio channels or audio streams using FFmpeg command. Can someone please help me with a ffmpeg command that can retain all the audio properties like audio count and retain the tracks unaltered(some ffmpeg commands that I have tried just picks one out of multiple streams and provides the output).

  


  Example scenario : I have a video file which has multi stream audio's (6 audio streams, 6 channel) file with audio format pcm, which was wrongly labelled as C C C C C C (when checked in media info - channel layout). But I need to change the labeling of audio tracks as L R C LFE Ls Rs (The desired audio codec is 5.1 (surround)).

  


  The scenarios that I have faced when trying to relabel this video file is :

  


  

  1. FFMpeg relabels correctly as L R C LFE Ls Rs, but it just takes one audio stream and places them in C channel (when checked in Audacity I can see the audio is present only in C channel), and leaves out other channels.

  


  2. Or it just merges all the audio streams into one (i.e.,the audio count becomes 1- media info output on the resulting file) resulting in a 5.1(LRC) audio codec- matrix.

  


  


  The command that got me close was

  


  ffmpeg -i input.mov -map 0:v -map 0:a:0 -c:a:0 copy -metadata:s:a:0 channel_layout="L" -map 0:a:1 -c:a:1 copy -metadata:s:a:1 channel_layout="R" -map 0:a:2 -c:a:2 copy -metadata:s:a:2 channel_layout="C" -map 0:a:3 -c:a:3 copy -metadata:s:a:3 channel_layout="LFE" -map 0:a:4 -c:a:4 copy -metadata:s:a:4 channel_layout="Ls" -map 0:a:5 -c:a:5 copy -metadata:s:a:5 channel_layout="Rs" -c:v copy output.mov"


  


  But output.mov file does not have any channel layout labeled to it (when checked in media info).

  


  Kindly help me with the proper command, so that I can convert the following file into a properly labeled (L R C LFE Ls Rs) 6 audio track, 5.1 (surround) file.

  


  Expecting a FFMpeg command to relabel the audio channel layout (in media info) from "C C C C C C" (array) to "L R C LFE Ls Rs" (array) and audio codec to be "5.1 (Surround)", audio count to be "6" retaining all video properties from parent file.

  


• fftools/ffmpeg : add InputStream.index

  19 mai 2023, par Anton Khirnov

  fftools/ffmpeg : add InputStream.index
  This allows to avoid access to the underlying AVStream in many places.
  

  • [DH] fftools/ffmpeg.c
  • [DH] fftools/ffmpeg.h
  • [DH] fftools/ffmpeg_dec.c
  • [DH] fftools/ffmpeg_demux.c
  • [DH] fftools/ffmpeg_filter.c
  • [DH] fftools/ffmpeg_mux_init.c

• Using libavformat to mux H.264 frames into RTP

  18 septembre 2021, par DanielB6

  I have an encoder that produces a series of H.264 I-frames and P-frames. I'm trying to use libavformat to mux and transmit these frames over RTP, but I'm stuck.

  



  My program sends RTP data, but the RTP timestamp increments by 1 each successive frame, instead of 90000/fps. It also doesn't look like it's doing the proper framing for H.264 NAL, since I can't decode the stream as H.264 in Wireshark.

  



  I suspect that I'm not setting up the codec information properly, but it appears in many places in the output format context, so it's unclear what exactly needs to be setup. The examples seem to all copy codec context info from encoders, which isn't my use case.

  



  This is what I'm trying :

  



  int main() {
    AVFormatContext context = avformat_alloc_context();

    if (!context) {
        printf("avformat_alloc_context failed\n");
        return;
    }

    AVOutputFormat *format = av_guess_format("rtp", NULL, NULL);

    if (!format) {
        printf("av_guess_format failed\n");
        return;
    }

    context->oformat = format;

    snprintf(context->filename, sizeof(context->filename), "rtp://%s:%d", "192.168.2.16", 10000);

    if (avio_open(&(context->pb), context->filename, AVIO_FLAG_READ_WRITE) < 0) {
        printf("avio_open failed\n");
        return;
    }

    stream = avformat_new_stream(context, NULL);

    if (!stream) {
        printf("avformat_new_stream failed\n");
        return;
    }

    stream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
    stream->codecpar->codec_id = AV_CODEC_ID_H264;
    stream->codecpar->width = 1920;
    stream->codecpar->height = 1080;

    avformat_write_header(context, NULL);

    ...
    write packets
    ...
}


  



  Example write packet :

  



  int write_packet(uint8_t *data, int size) {
    AVPacket p;
    av_init_packet(&p);
    p.data = buffer;
    p.size = size;
    p.stream_index = stream->index;

    av_interleaved_write_frame(context, &p);
}


  



  I've even went so far to build in libx264, find the encoder, and copy the codec context info from there into the stream codecpar, with the same result. My goal is to build without libx264, and any other libs that aren't required, but it isn't clear whether libx264 is required for defaults such as time base.

  



  How can the libavformat RTP muxer be initialized to properly send H.264 frames over RTCP+RTP ?