Can Closed Captions be preserved, transcoding MP4 to MP4

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iSAWaUFO
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Posts: 50
Joined: Wed Jan 02, 2008 3:45 am

Can Closed Captions be preserved, transcoding MP4 to MP4

Post by iSAWaUFO »

I want to transcode an existing MP4 file 640x368 to 480x272, to optimize the video file size for iPhone.
The MP4 includes optional Closed Captions (tx3g)
When I transcode the MP4, using HB 0.9.4, the Captions are not copied over to the smaller file.

Is there some way I can demux the captions from the 1st MP4 file and mux them into the copied file?
jamiemlaw
Veteran User
Posts: 536
Joined: Thu Sep 17, 2009 4:52 pm

Re: Can Closed Captions be preserved, transcoding MP4 to MP4

Post by jamiemlaw »

Subler should do the trick.
iSAWaUFO
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Joined: Wed Jan 02, 2008 3:45 am

Re: Can Closed Captions be preserved, transcoding MP4 to MP4

Post by iSAWaUFO »

Cool! Thanks.
Looks like Subler can bring over, not only the Closed Captions track but also the Chapters track from the previous MP4 file.
iSAWaUFO
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Posts: 50
Joined: Wed Jan 02, 2008 3:45 am

Re: Can Closed Captions be preserved, transcoding MP4 to MP4

Post by iSAWaUFO »

Now I'm wondering if there is a way to get the captions from a .MOV file.
Subler will not open .MOV
Sometimes I edit out commercials using SimpleMovieX, but the only way I can preserve captions after editing is to save as a .MOV file.
If I convert the .MOV to .MP4, the captions get lost and Subler can't open the .MOV.

Anyway to extract captions (tx3g) from an .MOV file?
Deleted User 11865

Re: Can Closed Captions be preserved, transcoding MP4 to MP4

Post by Deleted User 11865 »

iSAWaUFO wrote:Subler will not open .MOV
Subler can import tracks from QuickTime .mov files (though it can't open them directly).
kogyaru
Posts: 25
Joined: Sat Apr 14, 2007 1:29 am

Re: Can Closed Captions be preserved, transcoding MP4 to MP4

Post by kogyaru »

I'm in a bit of a snit. I want to extract captions, as the OP did -- but for the express purpose of converting the .tx3g file to SRT. I don't necessarily need it all done in one shot. I'm happy to extract the specific ttxt track, then convert it using whatever.

I am having trouble figuring out how to do this. Am wading through a number of command-line mp4 manipulation utilities, as well as Subler, and am stymied. Take a look at this:

Code: Select all

% mp4info MOVIE_DISC_1.m4v
mp4info version 1.6
MOVIE_DISC_1.m4v:
Track   Type    Info
1       video   H264 High@3, 456.230 secs, 5824 kbps, 720x480 @ 23.968174 fps
2       audio   MPEG-4 AAC LC, 456.234 secs, 164 kbps, 48000 Hz
3       audio   ac-3, 456.224 secs, 192 kbps, 48000 Hz
4       sbtl
 Tool: HandBrake svn3154 2010030701

% MP4Box -version
MP4Box - GPAC version 0.4.5 (build 33)
GPAC Copyright: (c) Jean Le Feuvre 2000-2005
                (c) ENST 2005-200X

% MP4Box -srt 4 MOVIE_DISC_1.m4v 
Track ID 4 is not a 3GPP text track

% MP4Box -raw 4 MOVIE_DISC_1.m4v
Extracting '' Track (type 'sbtl') - Compressor Unknown

% file *tx3g
MOVIE_DISC_1_track4.tx3g: data

% MP4Box -srt *tx3g
Unknown input file type
Error importing MOVIE_DISC_1_track4.tx3g: End Of Stream / File
What I'm seeing is a failure by this particular utility (MP4Box) to recognize the raw track 4 data as a 3GPP timed text file. Now, Subler lets me view the track, but not export it as a raw track. Any idea why I'm having trouble extracting the ttxt as a recognizable 3Gpp ttxt file?
kogyaru
Posts: 25
Joined: Sat Apr 14, 2007 1:29 am

Re: Can Closed Captions be preserved, transcoding MP4 to MP4

Post by kogyaru »

Well, I figured it out: older versions of MP4Box didn't recognize the 'sbtl' handler type, only 'text'. 0.4.6 (CVS) does.
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