[vlc] Re: Problem playing MPEG-PS files with mpeg4video

[Måns Rullgård]

Nico Sabbi <nsabbi at tiscali.it> writes:

> Måns Rullgård wrote:
>
>>Nico Sabbi <nsabbi at tiscali.it> writes:
>>
>>>Gildas Bazin wrote:
>>>
>>>>Ok, the main problem here is that we don't have access to the frame
>>>>rate information for this kind of streams so we can't really
>>>>interpolate the timestamps, thus we rely on each frame having at
>>>>least a DTS.
>>>>Do you know if there's a way to find out the frame rate info ?
>>>>
>>>this is what I implemented for mplayer:
>>>
>>>take 3 video frames and store
>>>- from the vol header the time_resolution
>>>- from the vop headers the 3 time_increments
>>>
>>>calculate the minimun difference between the 3 time_increments, say diff
>>>fps = timeinc_resolution / diff
>>>
>>>This method works also when there are b-frames because they have to be
>>>in the right order, e.g.
>>>
>>
>>You could also be nice to decoder and store the frame rate in the
>>PSM.  Have you tried whether VLC doing so makes VLC any happier?
>>
> VLC doesn't seem to be able to mux mpeg4 in mpeg-ps: the resululting files
> contain only audio.
> It would be nice to describe the framerate with a descriptor, but which?

The video stream descriptor seems suitable for this:

Syntax                                            No. of bits Mnemonic
video_stream_descriptor(){
          descriptor_tag                          8           uimsbf
          descriptor_length                       8           uimsbf
          multiple_frame_rate_flag                1           bslbf
          frame_rate_code                         4           uimsbf
          MPEG_1_only_flag                        1           bslbf
          constrained_parameter_flag              1           bslbf
          still_picture_flag                      1           bslbf
          if (MPEG_1_only_flag = = '0'){               
                     profile_and_level_indication 8           uimsbf
                     chroma_format                2           uimsbf
                     frame_rate_extension_flag    1           bslbf
                     reserved                     5           bslbf
          }
}

frame_rate_code ­ This is a 4-bit field as defined in 6.3.3 of ITU-T
Rec. H.262 | ISO/IEC 13818-2,

See TCVP for a sample implementation.

-- 
Måns Rullgård
mru at inprovide.com

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