[FFmpeg-devel] [PATCH]ffplay 2/2: Fix subtitle rendering for special cases

Robert Swain robert.swain
Mon Feb 9 01:27:54 CET 2009

2009/2/8 Bj?rn Axelsson <gecko at acc.umu.se>:
>>On Sun, 8 Feb 2009, Robert Swain wrote:
>>> 2009/2/6 Bj?rn Axelsson <gecko at acc.umu.se>:
>>> On Thu, 5 Feb 2009, Michael Niedermayer wrote:
>>>> > blend_subrect_2.diff:
>>>> > Fix blend_subrect for even-width subrects positioned on odd columns.
>>>> >
>>>> > When a subrect starts on an odd column, the first column is rendered
>>>> > separately and the chroma pointers are increased by one as if two
>>>> > columns
>>>> > were rendered. If the subrect had an even width to start width, the
>>>> > rest
>>>> > of the subrect has now an odd width and the final column is rendered
>>>> > separately, also increasing the chroma pointers as if two columns
>>>> > were
>>>> > rendered. This results in the chroma part of the subtitle getting
>>>> > offset
>>>> > one additional sample to the right for each row.
>>>> > The effect can be seen in the first, the sixth and the seventh
>>>> > subtitles
>>>> > of the sample[1].
>>>> this change looks wrong
>>> Here's a cleaner approach...
>>I'm not sure if I'm doing something wrong but I don't see any
>>subtitles when playing that sample using ffplay. What is required to
>>test this patch?
> Press t when playing to select the first subtitle stream.


Just as a note to Bj?rn, sometimes those subs in that clip have green
bits below the text so I'm guessing there's maybe some vertical issue
as well.

Best regards,

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