[FFmpeg-devel] [PATCH] movtextdec: MPEG4 Part 17 Timed Text Decoder.

Philip Langdale philipl at overt.org
Thu Jul 5 18:50:54 CEST 2012

On 05.07.2012 08:06, Yusuke Nakamura wrote:
> I don't recommend you use MPEG4 Part17 as the "short" form.
> MPEG-4 Part17 defines structure of __streaming__ timed text format.
> MPEG-4 Part17 refers to 3GPP TS 26.245 as one example to fragment 
> timed
> text sample into TTUs.
> (Streaming timed text access unit consists of concatenation of TTUs, 
> not
> simple text string + text modifiers.)
> Therefore, if you use MPEG-4 Part17, the decoder should extract text 
> sample
> (text string + text modifiers) and sample description from TTUs and 
> decode
> them, or just extract them.
> As long as this decoder decodes only 3GPP or QuickTime form timed 
> text
> stream, it is not an MPEG-4 Part17 decoder.

Yes, you make a very valid point. Man, this stuff makes my head hurt. I 
stick to "3GPP Timed Text" as the description. Do you have access to 
that actually use TTUs? I've never seen one or tools that will write 
them into
an mp4 container.



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