Getting VLC to play MXFlib op1a files
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Author:  Killertoffy [ Fri Nov 09, 2007 10:31 pm ]
Post subject:  Getting VLC to play MXFlib op1a files

I'm trying to find out what's needed to get VLC play some MXFlib wrappings.

Mpeg only frame wrapped op1a are ok.
Audio only frame wrapped op1a are almost ok, no sound because VLC sees no codec : "undefined". (see fix below)

However Mpeg+Audio doesn't work at all...
Any idea why ?

Fix to get VLC play op1a wav wrapped files :

in esp_wavpecm.cpp
// set Little endian order s16l
Ret->SetValue(SoundEssenceCompression_UL, DataChunk(16,SoundEssenceCompressionS16L_UL_Data));

in ulmap.h
const UInt8 SoundEssenceCompressionS16L_UL_Data[16] = {  0x06, 0x0e, 0x2b, 0x34, 0x04, 0x01, 0x01, 0x01, 0x04, 0x02, 0x02, 0x01, 0x7f, 0x00, 0x00, 0x00 };
const UL SoundEssenceCompressionS16L_UL(SoundEssenceCompressionS16L_UL_Data);


Author:  Killertoffy [ Sat Nov 10, 2007 2:04 pm ]
Post subject: 

I asked the ffmpeg team to give a look why it doesn't play and I got this :

Reimar Döffinger <> added the comment:

The header of that files gives the track ID for both sound and video
track as 0x15010501 (which is obviously nonsense since they can't both
have the same one).
The track ID of the actual audio track is 0x16010101, but that is
discarded since it is not in the headers.
I do not know the details of the specs but I would guess the file is broken.


More precisely, I think it violates SMPTE 379, section "7.3 Element to track

I'll give a look if I can find some tweak to get around this.

Author:  Matt Beard [ Mon Nov 19, 2007 12:18 pm ]
Post subject: 

You are right - this is a bug in mxfwrap.

To fix it:

Move this line ~1340 of mxfwrap.cpp:
         // The source will have be allocated a StreamID when added to the BodyStream - we need that for track linking later
         TrackInfoList.back()->EssenceID = Source->GetStreamID();

To just after this line at ~ 1360 of mxfwrap.cpp:
         // Add this stream to the body writer (first pass only)
         if(iTrack == 0) Writer->AddStream(Streams.front());

Then change:


in each of the siz AddxxxTrack() lines at ~1500 to 1530 of mxfwrap.cpp

Author:  Killertoffy [ Mon Dec 10, 2007 11:34 am ]
Post subject: 

Yes it does the job perfectly.

Thank you.

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