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• 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 ?

  


• FFMPEG convert file output without original file's extension [closed]

  26 juin 2020, par sknagu05

  @echo off

rem echo %~F0
rem echo %~F1

Set filename=%~F0
For %%A in ("%filename%") do (
    Set Folder=%%~dpA
    Set Name=%%~nxA
)

Set filename1=%~F1
For %%B in ("%filename1%") do (
    Set Folder1=%%~dpB
    Set Name1=%%~nxB
)

rem echo "%Folder1%"
rem echo "%Name1%"
rem pause

cd "%Folder1%"

TITLE Mp4 Video 1 Click - FFMPEG v.4.2.2 32-bit - Encode to HLS (software libx264)

set PATH=%Folder%;%SYSTEMROOT%\SysWOW64;%SYSTEMROOT%\System32


ffmpeg.exe -i "%Name1%" -profile:v baseline -level 3.0 -start_number 0 -hls_time 10 -hls_list_size 0 -f hls "%Name1%.m3u8"


  


• Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

  28 août 2020, par bbdangar

  I am using this library : com.arthenica:mobile-ffmpeg-full:4.4

  


  Getting this error message while running the command :

  


  final String command = "-y -i "+ inputPath +" -ar 22050 -hls_list_size 1000000 -hls_time 2 -s 640x360 " + outputPath;


  


  here is the complete code :

  


  private void convertVideo() {
        String inputPath = "/storage/emulated/0/Download/video.mp4";
        String outputPath = "/storage/emulated/0/Download/output.m3u8";
        final String command = "-y -i "+ inputPath +" -ar 22050 -hls_list_size 1000000 -hls_time 2 -s 640x360 " + outputPath;
        FFmpeg.executeAsync(command, new ExecuteCallback() {
            @Override
            public void apply(long executionId, int returnCode) {

                if (returnCode == RETURN_CODE_SUCCESS) {
                    Log.i(TAG, "Command execution completed successfully.");
                } else if (returnCode == RETURN_CODE_CANCEL) {
                    Log.i(TAG, "Command execution cancelled by user.");
                } else {
                    Log.i(TAG, String.format("Command execution failed with rc=%d and the output below.", returnCode));
                    Config.printLastCommandOutput(Log.INFO);
                }
            }
        });

    }


  


  here is output log :

  


  2020-08-28 07:05:59.355 10725-10820 W/mobile-ffmpeg: [graph 0 input from stream 0:0 @ 0xe2306c80] sws_param option is deprecated and ignored
2020-08-28 07:05:59.448 10725-10820 E/mobile-ffmpeg: [h264_v4l2m2m @ 0xcb442c00] can't configure encoder
2020-08-28 07:05:59.448 10725-10820 E/mobile-ffmpeg: Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
2020-08-28 07:05:59.463 10725-10820 I/mobile-ffmpeg: Conversion failed!
2020-08-28 07:05:59.465 10725-10725 I/mobile-ffmpeg: ffmpeg version v4.4-dev-416 Copyright (c) 2000-2020 the FFmpeg developers