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• avformat/matroskadec : Fix handling of huge default durations

  11 mai 2021, par Michael Niedermayer

  avformat/matroskadec : Fix handling of huge default durations
  Fixes : negation of -9223372036854775808 cannot be represented in type 'int64_t' (aka 'long') ; cast to an unsigned type to negate this value to itself
  
  Fixes : 33997/clusterfuzz-testcase-minimized-ffmpeg_dem_WEBM_DASH_MANIFEST_fuzzer-6752039691485184
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavformat/matroskadec.c

• avformat/dxa : Check fps to be within the supported range more precissely

  24 avril 2021, par Michael Niedermayer

  avformat/dxa : Check fps to be within the supported range more precissely
  Fixes : negation of -2147483648 cannot be represented in type 'int32_t' (aka 'int') ; cast to an unsigned type to negate this value to itself
  
  Fixes : assertion failure
  
  Fixes : 29102/clusterfuzz-testcase-minimized-ffmpeg_dem_DXA_fuzzer-6744985740378112
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavformat/dxa.c

• avformat_seek_file timestamps not using the correct time base

  19 juin 2021, par Charlie

  I am in the process of creating a memory loader for ffmpeg to add more functionality. I have audio playing and working, but am having an issue with avformat_seek_file timestamps using the wrong format.

  


  avformat.avformat_seek_file(file.context, -1, 0, timestamp, timestamp, 0)


  


  From looking at the docs it says if the stream index is -1 that the time should be based on AV_TIME_BASE. When I load the file through avformat_open_input with a null AVFormatContext and a filename, this works as expected.

  


  However when I create my own AVIOContext and AVFormatContext through avio_alloc_context and avformat_alloc_context respectively, the timestamps are no longer based on AV_TIME_BASE. When testing I received an access violation when I first tried seeking, and upon investigating, it seems that the timestamps are based on actual seconds now. How can I make these custom contexts time based on AV_TIME_BASE ?

  


  The only difference between the two are the custom loading of AVIOContext and AVFormatContext :

  


      data = fileobject.read()

    ld = len(data)

    buf = libavutil.avutil.av_malloc(ld)
    ptr_buf = cast(buf, c_char_p)

    ptr = ctypes.create_string_buffer(ld)
    memmove(ptr, data, ld)

    seeker = libavformat.ffmpeg_seek_func(seek_data)
    reader = libavformat.ffmpeg_read_func(read_data)
    writer = libavformat.ffmpeg_read_func(write_data)

    format = libavformat.avformat.avio_alloc_context(ptr_buf, buf_size, 0,
                                                     ptr_data,
                                                     reader,
                                                     writer,
                                                     seeker
                                                     )

    file.context = libavformat.avformat.avformat_alloc_context()
    file.context.contents.pb = format
    file.context.contents.flags |= AVFMT_FLAG_CUSTOM_IO

    result = avformat.avformat_open_input(byref(file.context),
                                          b"",
                                          None,
                                          None)

    if result != 0:
        raise FFmpegException('avformat_open_input in ffmpeg_open_filename returned an error opening file '
                              + filename.decode("utf8")
                              + ' Error code: ' + str(result))

    result = avformat.avformat_find_stream_info(file.context, None)
    if result < 0:
        raise FFmpegException('Could not find stream info')

    return file



  


  Here is the filename code that does work :

  


      result = avformat.avformat_open_input(byref(file.context),
                                          filename,
                                          None,
                                          None)
    if result != 0:
        raise FFmpegException('avformat_open_input in ffmpeg_open_filename returned an error opening file '
                              + filename.decode("utf8")
                              + ' Error code: ' + str(result))

    result = avformat.avformat_find_stream_info(file.context, None)
    if result < 0:
        raise FFmpegException('Could not find stream info')

    return file


  


  I am new to ffmpeg, but any help fixing this discrepancy is greatly appreciated.