Page 1 of 1
Can Closed Captions be preserved, transcoding MP4 to MP4
Posted: Sun Feb 28, 2010 4:21 pm
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?
Re: Can Closed Captions be preserved, transcoding MP4 to MP4
Posted: Tue Mar 02, 2010 9:55 am
by jamiemlaw
Subler should do the trick.
Re: Can Closed Captions be preserved, transcoding MP4 to MP4
Posted: Sat Mar 06, 2010 7:12 am
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.
Re: Can Closed Captions be preserved, transcoding MP4 to MP4
Posted: Wed Mar 10, 2010 1:11 am
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?
Re: Can Closed Captions be preserved, transcoding MP4 to MP4
Posted: Wed Mar 10, 2010 1:42 am
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).
Re: Can Closed Captions be preserved, transcoding MP4 to MP4
Posted: Thu Mar 11, 2010 7:28 pm
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?
Re: Can Closed Captions be preserved, transcoding MP4 to MP4
Posted: Fri Mar 12, 2010 1:00 pm
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.