[FFmpeg-user] QuickTime Player plays two audio tracks when I open a file transcoded with ffmpeg

Frank Häfemeier ffmpeg at frank.haefemeier.eu
Tue Nov 27 00:43:28 CET 2012


Am Montag, den 26.11.2012, 23:15 +0100 schrieb Gonzalo Suárez:
> Hi all.
> I'm having a weird behaviour when I open a file that was transcoded
> using ffmpeg. The command I used to transcode the file is the
> following:
> $ ffmpeg -i Collateral.vob -map 0:0 -map 0:30 -map 0:29 -preset
> ultrafast -crf 18 -vf crop=720:416 -profile:v high -ss 300 -t 30
> Collateral.mp4
> As you can see, I have two audio streams in the resulting mp4 file.
> When I open it in QuickTime Player and hit play, the audio of both
> streams is mixed. If I select View>Languages, none of the two streams
> is selected. If I select one of them, audio starts playing correctly.

I have the same behaviour if I try to look a video on my ipad. If there
are two different language streams in there, I have to select explicitly
a stream. Otherwise I will heard both. I hadn't thought about it,
but today I had another issue, which is related.
I tried to stream the video from my ipad to an Apple TV 2 (ATV2). And
now I heard nothing. But I found the reason and IMHO it has the same
root cause with your QuickTime player.
There was a recent change in ATV2 (got a hint from
http://www.videoredo.net/msgBoard/showthread.php?t=29620), the streams
must be grouped and only one stream should be enabled.
With the tool 'MP4Box' you can do this. If you call 'MP4Box -info
Collateral.mp4' it will create an output similar to this

  * Movie Info *
	Timescale 1000 - Duration 00:58:02.934
	Fragmented File no - 3 track(s)
	File suitable for progressive download (moov before mdat)
	File Brand isom - version 512
  File has no MPEG4 IOD/OD

  iTunes Info:
	Encoder Software: Lavf54.25.104

  Track # 1 Info - TrackID 1 - TimeScale 25 - Duration 00:58:02.920
  Media Info: Language "Undetermined" - Type "vide:avc1" - 87073 samples
  Visual Track layout: x=0 y=0 width=1024 height=576
  MPEG-4 Config: Visual Stream - ObjectTypeIndication 0x21
  AVC/H264 Video - Visual Size 720 x 576
	AVC Info: 1 SPS - 1 PPS - Profile High @ Level 3
	NAL Unit length bits: 32
	Pixel Aspect Ratio 64:45 - Indicated track size 1024 x 576

  Track # 2 Info - TrackID 2 - TimeScale 48000 - Duration 00:58:02.933
  Media Info: Language "German" - Type "soun:mp4a" - 163263 samples
  MPEG-4 Config: Audio Stream - ObjectTypeIndication 0x40
  MPEG-4 Audio MPEG-4 Audio AAC LC - 2 Channel(s) - SampleRate 48000
  Synchronized on stream 1
  Alternate Group ID 1

  Track # 3 Info - TrackID 3 - TimeScale 48000 - Duration 00:58:02.912
  Media Info: Language "German" - Type "soun:ac-3" - 108841 samples
	AC3 stream - Sample Rate 48000 - 2 channel(s) - bitrate 448000
  Alternate Group ID 1

You will see, ffmpeg had create the groups but both streams are enabled.
With the call 'MP4Box -disable 3 Collateral.mp4' you disable this audio
track. In my case this was the solution to hear again the audio on ATV2.

I don't know, if it is possible to do it with ffmpeg, but it would be
nice. I prefer to use only one tool.

Hope it helps.

P.S.: If you get an error message from 'MP4Box' like '[iso file]
Incomplete box ..w.' the reason could be a too old ffmpeg.

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