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• Revert "avformat/demux : Count EAGAIN as 100 bytes in relation to read limit in avform...

  18 juin 2022, par Marton Balint

  Revert "avformat/demux : Count EAGAIN as 100 bytes in relation to read limit in avformat_find_stream_info()"
  Modifying avformat_find_stream_info() behaviour based on the number of EAGAINs
  
  it encounters is a hack which usually only hides the real issue if such thing
  
  happen.
  This reverts commit b0cac7082d8a3ff2d4f039af01b45c48bb578de7.
  

  • [DH] libavformat/demux.c

• "method DESCRIBE failed : 401 Unauthorized" in Ffmpeg, yet VLC accepts the exact same RTSP URL

  30 septembre 2021, par IpsRich

  I've an RTSP URL that includes the username and password (i.e. of the form rtsp://username:password@server:554/path) and this works in VLC, but using this as an input to Ffmpeg, I get back the above DESCRIBE error and it aborts.

  


  I wondered if it might be the version of Ffmpeg I've got, but I used a fresh one via Docker (alfg/ffmpeg:latest) and the result was the same.

  


  Is there something I have to do, perhaps some extra information/hint I have to provide to Ffmpeg, to get it to accept the credentials and get past the DESCRIBE ? Or if it's the DESCRIBE bit that's the problem, can I get it to skip that (perhaps by providing all the source stream details manually) so that it doesn't fail ?

  


  I'd hoped that this might be the same problem, but it's not - my URL is quoted and doesn't contain anything like ? or *.

  


  (In case it has any bearing, I'm trying to take an RTSP stream that requires credentials, resize it on the fly using Ffmpeg, and "pipe" the new RTSP to RTSP Simple Server. Most of this I can do : it's just the credentials that are tripping me up.)

  


  UPDATE : One thing I didn't mention previously (because it didn't seem relevant) is that the RTSP stream comes from Milestone's Open Network Bridge server. It seems that ONB does not now allow URLs containing credentials, although this does not explain why the same URL works in VLC. Perhaps VLC extracts the credentials and provides them another way ? I've a support case open on this to try to get to the bottom of it. I'll update here if I discover anything helpful...

  


• Reasons for "Segmentation fault (core dumped)" when using Python extension and FFmpeg

  24 août 2021, par Christian Vorhemus

  I want to write a Python C extension that includes a function convertVideo() that converts a video from one format to another making use of FFmpeg 3.4.8 (the libav* libaries). The code of the extension is at the end of the question. The extension compiles successfully but whenever I open Python and want to call it (using a simple Python wrapper code that I don't include here), I get

  


  Python 3.7.10 (default, May  2 2021, 18:28:10)
[GCC 9.1.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import myModule
>>> myModule.convert_video("/home/admin/video.h264", "/home/admin/video.mp4")
convert 0
convert 1
Format raw H.264 video, duration -9223372036854775808 us
convert 2
Segmentation fault (core dumped)


  


  The interesting thing is, I wrote a simple helper program test_convert.cc that calls convertVideo() like so

  


  #include 
#include 

int convertVideo(const char *in_filename, const char *out_filename);

int main() {
  int res = convertVideo("/home/admin/video.h264", "/home/admin/video.mp4");
  return 0;
}


  


  and I compiled this program making use of the shared library that Python generates when building the C extension like so

  


  gcc test_convert.cc /usr/lib/python3.7/site-packages/_myModule.cpython-37m-aarch64-linux-gnu.so -o test_convert


  


  And it works ! The output is

  


  root# ./test_convert
convert 0
convert 1
Format raw H.264 video, duration -9223372036854775808 us
convert 2
convert 3
convert 4
convert 5
convert 6
Output #0, mp4, to '/home/admin/video.mp4':
    Stream #0:0: Video: h264 (High), yuv420p(tv, bt470bg, progressive), 1280x720 [SAR 1:1 DAR 16:9], q=2-31
convert 7


  


  The extension code looks like this

  


  #include 

#include 
#include 
#include 
#include 
#include 
#include 
#include 

extern "C"
{
#include "libavformat/avformat.h"
#include "libavutil/imgutils.h"
}

int convertVideo(const char *in_filename, const char *out_filename)
{
  // Input AVFormatContext and Output AVFormatContext
  AVFormatContext *input_format_context = avformat_alloc_context();
  AVPacket pkt;

  int ret, i;
  int frame_index = 0;
  printf("convert 0\n");
  av_register_all();
  printf("convert 1\n");
  // Input
  if ((ret = avformat_open_input(&input_format_context, in_filename, NULL,
                                 NULL)) < 0)
  {
    printf("Could not open input file.");
    return 1;
  }
  else
  {
    printf("Format %s, duration %lld us\n",
           input_format_context->iformat->long_name,
           input_format_context->duration);
  }
  printf("convert 2\n");
  if ((ret = avformat_find_stream_info(input_format_context, 0)) < 0)
  {
    printf("Failed to retrieve input stream information");
    return 1;
  }
  printf("convert 3\n");
  AVFormatContext *output_format_context = avformat_alloc_context();
  AVPacket packet;
  int stream_index = 0;
  int *streams_list = NULL;
  int number_of_streams = 0;
  int fragmented_mp4_options = 0;
  printf("convert 4\n");
  avformat_alloc_output_context2(&output_format_context, NULL, NULL,
                                 out_filename);
  if (!output_format_context)
  {
    fprintf(stderr, "Could not create output context\n");
    ret = AVERROR_UNKNOWN;
    return 1;
  }
  printf("convert 5\n");
  AVOutputFormat *fmt = av_guess_format(0, out_filename, 0);
  output_format_context->oformat = fmt;

  number_of_streams = input_format_context->nb_streams;
  streams_list =
      (int *)av_mallocz_array(number_of_streams, sizeof(*streams_list));

  if (!streams_list)
  {
    ret = AVERROR(ENOMEM);
    return 1;
  }
  for (i = 0; i < input_format_context->nb_streams; i++)
  {
    AVStream *out_stream;
    AVStream *in_stream = input_format_context->streams[i];
    AVCodecParameters *in_codecpar = in_stream->codecpar;
    if (in_codecpar->codec_type != AVMEDIA_TYPE_AUDIO &&
        in_codecpar->codec_type != AVMEDIA_TYPE_VIDEO &&
        in_codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE)
    {
      streams_list[i] = -1;
      continue;
    }
    streams_list[i] = stream_index++;

    out_stream = avformat_new_stream(output_format_context, NULL);
    if (!out_stream)
    {
      fprintf(stderr, "Failed allocating output stream\n");
      ret = AVERROR_UNKNOWN;
      return 1;
    }
    ret = avcodec_parameters_copy(out_stream->codecpar, in_codecpar);
    if (ret < 0)
    {
      fprintf(stderr, "Failed to copy codec parameters\n");
      return 1;
    }
  }
  printf("convert 6\n");
  av_dump_format(output_format_context, 0, out_filename, 1);
  if (!(output_format_context->oformat->flags & AVFMT_NOFILE))
  {
    ret = avio_open(&output_format_context->pb, out_filename, AVIO_FLAG_WRITE);
    if (ret < 0)
    {
      fprintf(stderr, "Could not open output file '%s'", out_filename);
      return 1;
    }
  }
  AVDictionary *opts = NULL;
  printf("convert 7\n");
  ret = avformat_write_header(output_format_context, &opts);
  if (ret < 0)
  {
    fprintf(stderr, "Error occurred when opening output file\n");
    return 1;
  }
  int n = 0;

  while (1)
  {
    AVStream *in_stream, *out_stream;
    ret = av_read_frame(input_format_context, &packet);
    if (ret < 0)
      break;
    in_stream = input_format_context->streams[packet.stream_index];
    if (packet.stream_index >= number_of_streams ||
        streams_list[packet.stream_index] < 0)
    {
      av_packet_unref(&packet);
      continue;
    }
    packet.stream_index = streams_list[packet.stream_index];

    out_stream = output_format_context->streams[packet.stream_index];

    out_stream->codec->time_base.num = 1;
    out_stream->codec->time_base.den = 30;

    packet.pts = n * 3000;
    packet.dts = n * 3000;
    packet.duration = 3000;

    packet.pos = -1;

    ret = av_interleaved_write_frame(output_format_context, &packet);
    if (ret < 0)
    {
      fprintf(stderr, "Error muxing packet\n");
      break;
    }
    av_packet_unref(&packet);
    n++;
  }

  av_write_trailer(output_format_context);
  avformat_close_input(&input_format_context);
  if (output_format_context &&
      !(output_format_context->oformat->flags & AVFMT_NOFILE))
    avio_closep(&output_format_context->pb);
  avformat_free_context(output_format_context);
  av_freep(&streams_list);
  if (ret < 0 && ret != AVERROR_EOF)
  {
    fprintf(stderr, "Error occurred\n");
    return 1;
  }
  return 0;
}
// PyMethodDef and other orchestration code is skipped


  


  What is the reason that the code works as expected in my test_convert but not within Python ?