The VideoLAN Forums

Posted: **17 Aug 2010 22:13**

Hi all guys, i'm using vlc 1.1.2 and i noted that vlc doesn't show the name of the video/audio tracks of an mp4 container(neither in the track selection nor in the codec details) as it does with an mkv. In case of an mp4 container, vlc only shows the language type.
Is there a fix for this?

Posted: **17 Aug 2010 23:53**

I second that, that would be nice

As you said, VLC can already do it for MKV so why not for MP4 as well ?

Posted: **19 Aug 2010 16:20**

Well, at least i think someone around here saw this post, so... i'm hoping for a fix, if possible.
bye

Posted: **19 Aug 2010 16:26**

What atom?

Posted: **19 Aug 2010 16:33**

What atom?

If i'm not wrong, should be the hdlr atom for the tracks

Posted: **19 Aug 2010 16:50**

which is the handler, not the name.

Posted: **19 Aug 2010 17:56**

Do you mean the atom at which hdlr belongs to?

Posted: **19 Aug 2010 18:20**

which is the handler, not the name.

With a MP4 file muxed and tagged with MP4Box being compliant with the MPEG-4 Base Media ISOM standard where the video track is named "H.264/AVC Video" and the audio track is named "AAC LC Audio" we can get the following information:

That's from VLC messages log:

Code: Select all

mp4 debug: found Box: hdlr size 48
mp4 debug: read box: "hdlr" handler type vide name H.264/AVC Video
mp4 debug: found Box: hdlr size 45
mp4 debug: read box: "hdlr" handler type soun name AAC LC Audio

And when using MP4v2 trunk-r355 tools:

That's from MP4file tool:

Code: Select all

    type hdlr (moov.trak.mdia.hdlr)
     version = 0 (0x00)
     flags = 0 (0x000000)
     reserved1 = <4 bytes>  00 00 00 00  |....|
     handlerType = vide
     reserved2 = <12 bytes>  00 00 00 00 00 00 00 00 00 00 00 00  |............|
     name = H.264/AVC Video
    type hdlr (moov.trak.mdia.hdlr)
     version = 0 (0x00)
     flags = 0 (0x000000)
     reserved1 = <4 bytes>  00 00 00 00  |....|
     handlerType = soun
     reserved2 = <12 bytes>  00 00 00 00 00 00 00 00 00 00 00 00  |............|
     name = AAC LC Audio

That's from MP4track tool:

Code: Select all

track[0] id=1
  type           = video
  enabled        = true
  inMovie        = false
  inPreview      = false
  layer          = 0
  alternateGroup = 0
  volume         = 0.0000
  width          = 480.00000000
  height         = 360.00000000
  language       = English
  handlerName    = H.264/AVC Video
  userDataName   = <absent>
track[1] id=2
  type           = audio
  enabled        = true
  inMovie        = false
  inPreview      = false
  layer          = 0
  alternateGroup = 0
  volume         = 1.0000
  width          = 0.00000000
  height         = 0.00000000
  language       = English
  handlerName    = AAC LC Audio
  userDataName   = <absent>

Posted: **22 Aug 2010 18:30**

I'm sorry, i can't tell you more detailed information because i don't know much of mp4 implementation, however, saying track names, i'm refering to those names that you set through mp4box (with the syntax -add video.h264:name=TrackName) while adding tracks before muxing. That 'TrackName' is written inside the component name field of the handler reference atom contained in the mdia atom(just after the mdhd atom). Various programs(like media info etc.) report that strings as video/audio name(or title, something like that).
It would be nice to show that name when you select a track in a mp4 with multiple tracks(like vlc does with mkv as i said).
It's not a real bug, but only a detail that could be useful for people(like me

) that handle mp4 files.

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