How to replace avcodec_encode_audio2()/avcodec_encode_video2() with avcodec_send_frame() and avcodec_receive_packet()?

Question

In muxing example in link am attempting to use avcodec_send_frame() and avcodec_receive_packet() instead of avcodec_encode_audio2()/avcodec_encode_video2() as they are deprecated. In

  352     ret = avcodec_encode_audio2(c, &pkt, frame, &got_packet);
  353     if (ret < 0) {
  354         fprintf(stderr, "Error encoding audio frame: %s\n", av_err2str(ret));
  355         exit(1);
  356     }
  357 
  358     if (got_packet) {
  359         ret = write_frame(oc, &c->time_base, ost->st, &pkt);
  360         if (ret < 0) {
  361             fprintf(stderr, "Error while writing audio frame: %s\n",
  362                     av_err2str(ret));
  363             exit(1);
  364         }
  365     }
  366 
  367     return (frame || got_packet) ? 0 : 1;

and in

  522     ret = avcodec_encode_video2(c, &pkt, frame, &got_packet);
  523     if (ret < 0) {
  524         fprintf(stderr, "Error encoding video frame: %s\n", av_err2str(ret));
  525         exit(1);
  526     }
  527 
  528     if (got_packet) {
  529         ret = write_frame(oc, &c->time_base, ost->st, &pkt);
  530     } else {
  531         ret = 0;
  532     }
  533 
  534     if (ret < 0) {
  535         fprintf(stderr, "Error while writing video frame: %s\n", av_err2str(ret));
  536         exit(1);
  537     }
  538 
  539     return (frame || got_packet) ? 0 : 1;

What to assign got_packet variable with when using avcodec_send_frame() and avcodec_receive_packet() functions and how to change the code if I do?. I have tried this so far

ret = avcodec_send_frame(c, frame);
if (ret < 0) {
    fprintf(stderr, "Error sending the frame to the audio encoder\n");
    exit(1);
}
if (ret = 0) {
    got_packet = avcodec_receive_packet(c, &pkt);
    if (got_packet == AVERROR(EAGAIN) || got_packet == AVERROR_EOF){
        fprintf(stderr, "Error receiving packet\n");
        return -1;}
    else if (got_packet < 0) {
        fprintf(stderr, "Error encoding audio frame\n");
        exit(1);
    }
    ret1 = write_frame(oc, &c->time_base, ost->st, &pkt);
    if (ret1 < 0) {
        fprintf(stderr, "Error while writing audio frame: %s\n",
                av_err2str(ret1));
        exit(1);
    }
    av_packet_unref(&pkt);
}
return (frame || got_packet) ? 0 : 1;

but isn't working and am having hard time getting it to work.

With a quick look, I couldn't spot what's wrong. If you put your project somewhere (like github) for linux with makefile + the sample audio file. I can check it to see whats wrong. — the kamilz, Jan 02 '20 at 07:31
@thekamilz I have provided the link to muxing.c in the question. Sample audio is not needed. The functions get_audio_frame(), open_audio() generates dummy audio frames and fill_yuv_image() generates dummy video frames. Am running it on ubuntu with command `gcc muxing.c -o muxing -lm -lavformat -lavcodec -lavutil -lswscale -lz -lswresample` — Optic_Ray, Jan 03 '20 at 06:51
Ok, I see. It looks like `muxing.c` example uses old api. Perhaps you should check `encode_audio.c` and `encode_video.c` in this link: https://ffmpeg.org/doxygen/trunk/examples.html which uses new API. — the kamilz, Jan 03 '20 at 07:30

score 4 · Accepted Answer · edited Oct 27 '20 at 15:30

In avcodec_encode_video2(), got_packet_ptr will be 0 when output packet is empty. The got_packet_ptr will equal 1 when output packet is non-empty and during draining mode (at end-of-file situations) when NULL is sent to avcodec_encode_video2() until all buffered items are flushed after which it becomes 0 again.

In new API, return value from avcodec_receive_packet() will be equal to 0 when buffer is full or when draining mode is entered, which is similar to got_packet_ptr being equal to 1. The avcodec_receive_packet() otherwise returns negative error code AVERROR(EAGAIN) which means output is not available in the current state - user must try to send input or AVERROR_EOF i.e, the encoder has been fully flushed, and there will be no more output packets.

Using the new API in muxing.c example in the following way worked for me:

ret = avcodec_send_frame(c, frame);
if (ret < 0) {
    fprintf(stderr, "Error sending a frame for encoding\n");
    exit(1);
}
while (ret >= 0) {
    ret = avcodec_receive_packet(c, &pkt);
    if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF){
        return (ret==AVERROR(EAGAIN)) ? 0:1;
     }
    else if (ret < 0) {
        fprintf(stderr, "Error during encoding\n");
        exit(1);
    }
    ret = write_frame(oc, &c->time_base, ost->st, &pkt);
    if (ret < 0) {
       fprintf(stderr, "Error while writing video frame: %s\n", av_err2str(ret));
       exit(1);
    }
    av_packet_unref(&pkt);
}
return (frame) ? 0 : 1;

Can you please tell me, why do we sit in a while loop ```while(ret >=0)``` and not in an ```if``` condition :) ? — Vivekanand V, Sep 07 '21 at 03:09
A side-by-side example of replacement can be found here: https://github.com/ferdymercury/amide/pull/23/files — ferdymercury, Jul 09 '22 at 09:03
Also useful: https://blog.fearcat.in/a?ID=01000-97990449-e9f9-4b26-839a-b8c4cad60efa — ferdymercury, Jul 09 '22 at 09:04

How to replace avcodec_encode_audio2()/avcodec_encode_video2() with avcodec_send_frame() and avcodec_receive_packet()?

1 Answers1