[FFmpeg-user] Which command line can do dvb_teletext from ts to mp4

Marton Balint cus at passwd.hu
Wed Feb 17 20:32:05 CET 2016

On Tue, 16 Feb 2016, Henk D. Schoneveld wrote:

> On 16 Feb 2016, at 14:40, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
>> Henk D. Schoneveld <belcampo <at> zonnet.nl> writes:
>>>  Stream #0:5 -> #0:2 (dvb_teletext (libzvbi_teletextdec)
>>> -> mov_text (native))
>>> Error while opening encoder for output stream #0:2 - 
>>> maybe incorrect parameters such as bit_rate, rate,
>>> width or height
>> It seems that this is only the effect of my incorrect 
>> autodetection patch, it works for samples with 
>> correctly signaled teletext.
>> You could try the patch Marton posted today (instead of 
>> mine):
>> "avformat/dvbtxt: add raw demuxer for dvb teletext probing”

> I applied the patch, behaviour the same. My probably/maybe ‘crippled’ source files work fine with telxcc/srt and ffmpeg as long as ass and mkv as destination are chosen.
> What I don’t understand is what makes ass -> mkv work and mov_text -> mp4 fail. 
> What is the relation between one and the other. ffmpeg can decode dvb_teletext, is able to put it in ass format and NOT in mov_text format. It doesn’t make much sense to me.

Okay, I think I hunted this down, the problem is that the probed dvb 
teletext stream is only detected during avformat_find_stream_info and is 
not present after avformat_open_input, therefore it has no options set, so 
the codec defaults to a bitmap output, which has no 
avctx->subtitle_header, therefore mov_text encoding fails.

I'll submit a patch which changes the order of initializations in ffmpeg.c 
and fixes this issue.


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