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Old 13th May 2010, 15:39   #1  |  Link
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Extracting timecodes from an mp4/h264 under linux

Im trying to transcode some mp4s on my linux machine. Basically I want to transcode an mp4 (h264) video into a lower bitrate for the purposes of streaming on the web. Simple eh?

The problem starts when my mp4 has a variable frame rate (VFR) and it seems there is no fully linux way (that works) of extracting the timecodes from the video stream.

I use a program called DTSEdit.exe on windows to achieve this and there isnít a linux version knocking round on the internet.
Once I have this timecode file I then use tc2mp4.pl to convert the timecode file into NHML which mp4box can consume when creating the new mp4 (as per http://forum.doom9.org/showthread.php?t=112199 )

Ive tried using MP4Box Ėnhml to extract the data from the original mp4 but mp4box produces soemthing that when reimported behaves as if its a constant frame rate - i.e. doesnt work.

Does anyone have a fully linux way of extracting the timecodes from an mp4 so I donít have to resort to using wine and doing it that way? Id really appreciate any help on this one!

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Old 13th May 2010, 15:57   #2  |  Link
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Maybe I'm missing something, but it seems like HandBrake and probably x264 all by itself could do a VFR mp4->mp4 transcode.
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Old 13th May 2010, 17:41   #3  |  Link
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Old 29th May 2010, 03:36   #4  |  Link
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Related to this:

I see that x264 now supports VFR ratecontrol. I'm wondering if this provides any benefit as opposed to my current DVD rip workflow:

rip DVD to .vob
run .vob through dgindex to get .d2v file
feed AVS script into x264.exe; AVS script looks like -> load .d2v, mpeg2 decoding/telecide/decimate, produce timecodes.txt
mux with mkvmerge; feed in timecodes.txt

Would the main difference be that I could cut out the timecodes.txt stuff and just run some additional parameters to x264.exe instead? Is there even any point in doing so?
smooth_hands is offline   Reply With Quote

linux mp4 vfr

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