[FFmpeg-devel] [vf_ass.c] 2 lines of code that need your attention

REN Lifeng renlifeng at wowfly.com
Tue Mar 20 06:29:09 CET 2012

Stefano Sabatini <stefasab at gmail.com> writes:

> On date Friday 2012-03-16 10:03:29 +0800, REN Lifeng encoded:
>> Hi developer of the ASS/SSA video filter,
> Hi.
> [...]
>> 2. aspec ratiot of video  v.s. aspect ratio of display
>> 146:    ass_set_aspect_ratio(ass->renderer, dar, sar);
>>  * \param dar display aspect ratio (DAR), prescaled for output PAR
>> I has a Karaoke vedio with size of 640x272 and a subtitle in ASS format.
>> With line 146, there are cases where multiple words changes color
>> simultaneously. This should not happen. And this problem will not arise
>> if we play the video and subtitle with Mplayer. And it will not arise if
>> we remove line 146 from vf_ass.c.
>> To provide more details, I also the following comparation. With
>> attatched subtitle, test1 generate 22 images among which only one
>> Chinese character is split. test2 generate 23 images where 2 characters
>> are split. You may need some Chinese fonts to reproduce the problem.
> Check attached patch and tell me if it works for you. The simple
> solution is to simply set the dar to 1.0, but since we like nifty
> switches and buttons, it is making it configurable.

I have checked the patch. The defaults works for me. Setting dar to 1.3
(ass=x.ass:dar=1.3) also works for me. Thanks!

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