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• Error while using h264_cuvid decoder with ffmpeg

  8 octobre 2023, par tthibalti

  I am trying to decode a video using the NVIDIA cuvid hardware acceleration with ffmpeg.

  


  I am using a NVIDIA GeForce GT 745M Graphics card (GPU:GK107), which is compatible with cuvid as specified by NVIDIA here

  


  I compiled ffmpeg with the following flags :

  


  ./configure --enable-cuda --enable-nvenc --enable-cuvid


  


  Then, I used ffmpeg with the following command line :

  


  ffmpeg.exe -hwaccel cuvid -c:v h264_cuvid -i video.mkv video.mkv


  


  ffmpeg finishes and seems to be unable to open cuvid functions :

  


  Cannot load cuvidGetDecoderCaps
[h264_cuvid @ 07047b80] Failed loading nvcuvid.
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (h264_cuvid) -> h264 (libx264))
  Stream #0:1 -> #0:1 (ac3 (native) -> vorbis (libvorbis))
  Stream #0:3 -> #0:2 (subrip (srt) -> ass (ssa))
Error while opening decoder for input stream #0:0 : Unknown error occurred


  


  In ffmpeg source code, I can find out that this error message is printed by the following macro :

  


  #define LOAD_SYMBOL(fun, tp, symbol)                                \
    do {                                                            \
        if (!((f->fun) = (tp*)dlsym(f->lib, symbol))) {             \
            av_log(NULL, AV_LOG_ERROR, "Cannot load %s\n", symbol); \
            ret = AVERROR_UNKNOWN;                                  \
            goto error;                                             \
        }                                                           \
        av_log(NULL, AV_LOG_TRACE, "Loaded sym: %s\n", symbol);     \
    } while (0)


  


  Which is called by :

  


  static inline int cuvid_load_functions(CuvidFunctions **functions)
{
    GENERIC_LOAD_FUNC_PREAMBLE(CuvidFunctions, cuvid, NVCUVID_LIBNAME);

    LOAD_SYMBOL(cuvidGetDecoderCaps, tcuvidGetDecoderCaps, "cuvidGetDecoderCaps");
    LOAD_SYMBOL(cuvidCreateDecoder, tcuvidCreateDecoder, "cuvidCreateDecoder");
    LOAD_SYMBOL(cuvidDestroyDecoder, tcuvidDestroyDecoder, "cuvidDestroyDecoder");
    LOAD_SYMBOL(cuvidDecodePicture, tcuvidDecodePicture, "cuvidDecodePicture");
#ifdef __CUVID_DEVPTR64
    LOAD_SYMBOL(cuvidMapVideoFrame, tcuvidMapVideoFrame, "cuvidMapVideoFrame64");
    LOAD_SYMBOL(cuvidUnmapVideoFrame, tcuvidUnmapVideoFrame, "cuvidUnmapVideoFrame64");
#else
    LOAD_SYMBOL(cuvidMapVideoFrame, tcuvidMapVideoFrame, "cuvidMapVideoFrame");
    LOAD_SYMBOL(cuvidUnmapVideoFrame, tcuvidUnmapVideoFrame, "cuvidUnmapVideoFrame");
#endif
    LOAD_SYMBOL(cuvidCtxLockCreate, tcuvidCtxLockCreate, "cuvidCtxLockCreate");
    LOAD_SYMBOL(cuvidCtxLockDestroy, tcuvidCtxLockDestroy, "cuvidCtxLockDestroy");
    LOAD_SYMBOL(cuvidCtxLock, tcuvidCtxLock, "cuvidCtxLock");
    LOAD_SYMBOL(cuvidCtxUnlock, tcuvidCtxUnlock, "cuvidCtxUnlock");

    LOAD_SYMBOL(cuvidCreateVideoSource, tcuvidCreateVideoSource, "cuvidCreateVideoSource");
    LOAD_SYMBOL(cuvidCreateVideoSourceW, tcuvidCreateVideoSourceW, "cuvidCreateVideoSourceW");
    LOAD_SYMBOL(cuvidDestroyVideoSource, tcuvidDestroyVideoSource, "cuvidDestroyVideoSource");
    LOAD_SYMBOL(cuvidSetVideoSourceState, tcuvidSetVideoSourceState, "cuvidSetVideoSourceState");
    LOAD_SYMBOL(cuvidGetVideoSourceState, tcuvidGetVideoSourceState, "cuvidGetVideoSourceState");
    LOAD_SYMBOL(cuvidGetSourceVideoFormat, tcuvidGetSourceVideoFormat, "cuvidGetSourceVideoFormat");
    LOAD_SYMBOL(cuvidGetSourceAudioFormat, tcuvidGetSourceAudioFormat, "cuvidGetSourceAudioFormat");
    LOAD_SYMBOL(cuvidCreateVideoParser, tcuvidCreateVideoParser, "cuvidCreateVideoParser");
    LOAD_SYMBOL(cuvidParseVideoData, tcuvidParseVideoData, "cuvidParseVideoData");
    LOAD_SYMBOL(cuvidDestroyVideoParser, tcuvidDestroyVideoParser, "cuvidDestroyVideoParser");

    GENERIC_LOAD_FUNC_FINALE(cuvid);
}


  


  Does anybody know if a specific file is needed by cuvid to load its functions ?
Any clue to what is wrong here ?

  


• Can you think of a reason why windows might not enable audio if noone is logged in ?

  3 juillet 2017, par Caius Jard

  I’m having a bizarre problem with some virtual servers created to record podcasts. They run on amazon AWS as windows server 2012 instances and a small c# app tells FFMPEG to do the heavy lifting of capturing from the virtual screen and reading from the virtual sound card (Virtual Audio Cable : https://en.wikipedia.org/wiki/Virtual_Audio_Cable) via DirectShow filters

  The problem I have is if I leave the machine to do its stuff unattended, the recordings are sometimes silent. If I log in via VNC and watch it doing its stuff the audio is recorded just fine. All other aspects of the test op are the same, and the virtual machine is shut down between successive recordings so each one should theoretically be a clean slate. The app runs under a logged in session (hence the use of VNC rather than RDP)

  I’m now wondering if there is some optimisation of the windows sound engine whereby it doesn’t bother playing audio if it thinks noone is listening. The confusing thing to me is that not every virtual machine suffers these problems ; some of them record fine (and they’re all created from the same seed virtual hard disk image) in unattended mode

  I’m asking this question with the aim of getting together a list of things I can check/look into/debug.. I don’t have much knowledge of how MME/DirectSound/WASAPI work internally...

• ffmpeg failed to call avcodec_send_packet

  23 juin 2017, par Gizak

  Windows 10 x64,
  ffmpeg : 3.1, prebuilt dlls

  Absolute beginner here.

  I was trying out a very basic case to decode frames from a video file but desperately failed at every attempts. The final code snippet looks like this :

  #define __STDC_CONSTANT_MACROS
  
  extern "C" {
  
  #include<libavutil></libavutil>avutil.h>
  
  #include<libavutil></libavutil>imgutils.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libswscale></libswscale>swscale.h>
  
  }
  
  
  
  #include <iostream>
  
  
  
  
  
  int main(int argc, char **argv) {
  
      AVFormatContext* ctx_format = nullptr;
  
      AVCodecContext* ctx_codec = nullptr;
  
      AVCodec* codec = nullptr;
  
      AVFrame* frame = av_frame_alloc();
  
      int stream_idx;
  
      SwsContext* ctx_sws = nullptr;
  
      const char* fin = argv[1];
  
      AVStream *vid_stream = nullptr;
  
      AVPacket* pkt = av_packet_alloc();
  
  
  
      av_register_all();
  
  
  
      if (int ret = avformat_open_input(&amp;ctx_format, fin, nullptr, nullptr) != 0) {
  
          std::cout &lt;&lt; 1 &lt;&lt; std::endl;
  
          return ret;
  
      }
  
      if (avformat_find_stream_info(ctx_format, nullptr) &lt; 0) {
  
          std::cout &lt;&lt; 2 &lt;&lt; std::endl;
  
          return -1; // Couldn't find stream information
  
      }
  
      av_dump_format(ctx_format, 0, fin, false);
  
  
  
      for (int i = 0; i &lt; ctx_format->nb_streams; i++)
  
          if (ctx_format->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
  
              stream_idx = i;
  
              vid_stream = ctx_format->streams[i];
  
              break;
  
      }
  
      if (vid_stream == nullptr) {
  
          std::cout &lt;&lt; 4 &lt;&lt; std::endl;
  
          return -1;
  
      }
  
  
  
      codec = avcodec_find_decoder(vid_stream->codecpar->codec_id);
  
      if (!codec) {
  
          fprintf(stderr, "codec not found\n");
  
          exit(1);
  
      }
  
      ctx_codec = avcodec_alloc_context3(codec);
  
  
  
      if(avcodec_parameters_to_context(ctx_codec, vid_stream->codecpar)&lt;0)
  
          std::cout &lt;&lt; 512;
  
      if (avcodec_open2(ctx_codec, codec, nullptr)&lt;0) {
  
          std::cout &lt;&lt; 5;
  
          return -1;
  
      }
  
  
  
      //av_new_packet(pkt, pic_size);
  
  
  
      while(av_read_frame(ctx_format, pkt) >= 0){
  
          int ret = avcodec_send_packet(ctx_codec, pkt);
  
          if (ret &lt; 0 || ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
  
              std::cout &lt;&lt; "avcodec_send_packet: " &lt;&lt; ret &lt;&lt; std::endl;
  
              break;
  
          }
  
          if (pkt->stream_index == stream_idx) {
  
              while (ret  >= 0) {
  
                  ret = avcodec_receive_frame(ctx_codec, frame);
  
                  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
  
                      //std::cout &lt;&lt; "avcodec_receive_frame: " &lt;&lt; ret &lt;&lt; std::endl;
  
                      break;
  
                  }
  
                  std::cout &lt;&lt; "frame: " &lt;&lt; ctx_codec->frame_number &lt;&lt; std::endl;
  
              }
  
          }
  
          av_packet_unref(pkt);
  
      }
  
  
  
      avformat_close_input(&amp;ctx_format);
  
      av_packet_unref(pkt);
  
      avcodec_free_context(&amp;ctx_codec);
  
      avformat_free_context(ctx_format);
  
      return 0;
  
  }
  
  </iostream>

  It basically leaves everything by its defaults and try to read packets and decode frames from them. The avcodec_send_packet always returned a negative value at the first or second round of calling in the while loop.

  Output for flv :

  > .\streamer_test.exe .\SampleVideo_360x240_5mb.flv
  
  Input #0, flv, from '.\SampleVideo_360x240_5mb.flv':
  
    Metadata:
  
      encoder         : Lavf53.24.2
  
    Duration: 00:00:53.32, start: 0.000000, bitrate: 787 kb/s
  
      Stream #0:0: Audio: aac (LC), 48000 Hz, 5.1, fltp, 384 kb/s
  
      Stream #0:1: Video: flv1, yuv420p, 320x240, 500 kb/s, 1k fps, 25 tbr, 1k tbn
  
  frame: 1
  
  [flv @ 000001545edb66c0] Bad picture start code
  
  [flv @ 000001545edb66c0] header damaged
  
  avcodec_send_packet: -1094995529

  Output for mp4 :

  > .\streamer_test.exe .\SampleVideo_360x240_10mb.mp4
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '.\SampleVideo_360x240_10mb.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      creation_time   : 1970-01-01T00:00:00.000000Z
  
      encoder         : Lavf53.24.2
  
    Duration: 00:02:05.95, start: 0.000000, bitrate: 669 kb/s
  
      Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 320x240 [SAR 1:1 DAR 4:3], 282 kb/s, 15 fps, 15 t
  
  br, 15360 tbn, 30 tbc (default)
  
      Metadata:
  
        creation_time   : 1970-01-01T00:00:00.000000Z
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 5.1, fltp, 383 kb/s (default)
  
      Metadata:
  
        creation_time   : 1970-01-01T00:00:00.000000Z
  
        handler_name    : SoundHandler
  
  [h264 @ 000002e2446a6cc0] Invalid NAL unit size (17191968 > 1007).
  
  [h264 @ 000002e2446a6cc0] Error splitting the input into NAL units.
  
  avcodec_send_packet: -1094995529

  Output for mkv :

  > .\streamer_test.exe .\SampleVideo_1280x720_2mb.mkv
  
  Input #0, matroska,webm, from '.\SampleVideo_1280x720_2mb.mkv':
  
    Metadata:
  
      ENCODER         : Lavf53.24.2
  
    Duration: 00:00:10.65, bitrate: 1575 kb/s
  
      Stream #0:0: Video: mpeg4 (Simple Profile), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 1k tbn, 25 tbc (de
  
  fault)
  
      Stream #0:1: Audio: aac (LC), 48000 Hz, 5.1, fltp (default)
  
  frame: 1
  
  [mpeg4 @ 000001166798ede0] header damaged
  
  avcodec_send_packet: -1

  So I guess there must be something wrong around avcodec_send_packet call but could not figured out what is missing. Any ideas about the causes ? Much appreciate your help !