[FFmpeg-devel] [PATCH] lavf/avienc: New AVOption write_keyframe_palette

[Ronald S. Bultje]

Hi,

On Tue, Mar 8, 2016 at 7:48 AM, Mats Peterson <
matsp888-at-yahoo.com at ffmpeg.org> wrote:

> On 03/08/2016 01:44 PM, Mats Peterson wrote:
>
>> On 03/08/2016 01:43 PM, Ronald S. Bultje wrote:
>>
>>> Hi Mats,
>>>
>>> On Mon, Mar 7, 2016 at 8:59 PM, Mats Peterson <
>>> matsp888-at-yahoo.com at ffmpeg.org> wrote:
>>>
>>> On 03/07/2016 07:48 PM, Mats Peterson wrote:
>>>>
>>>> On 03/07/2016 07:43 PM, Mats Peterson wrote:
>>>>>
>>>>> Here's a somewhat experimental patch with a new AVOption
>>>>>> write_keyframe_palette that allows you to write the palette to every
>>>>>> keyframe. It is disabled by default, but it is needed for any file
>>>>>> that
>>>>>> contains palette changes.
>>>>>>
>>>>>>
>>>>>> It is needed in order to switch palette properly when seeking, that
>>>>> is.
>>>>>
>>>>>
>>>>> It's interesting to note that Windows Media Player doesn't need xxpc
>>>> chunks at keyframes in order to seek properly in the following original
>>>> file from Sierra's King's Quest VI. I have of course no idea how they
>>>> solve
>>>> that.
>>>>
>>>> This original file doesn't work properly in FFplay for some reason. It
>>>> generates "stream_ptr out of bounds" messages at the locations of the
>>>> xxpc
>>>> chunks.
>>>>
>>>> File:
>>>> https://drive.google.com/open?id=0B3_pEBoLs0faaFY0ME92SDA1VEU
>>>>
>>>
>>>
>>> Please don't wrote so many messages in response to yourself.
>>>
>>> If you want, I can look at the file. My assumption is that it either
>>> indexes or otherwise caches the xxpc chunks so it knows what the last
>>> xxpc
>>> before-or-on each keyframe seekpoint is. That should be trivial to do in
>>> our demuxer also.
>>>
>>> Ronald
>>> _______________________________________________
>>>
>>
>> It would be nice if you could have a look at it, Ronald, when you have
>> the time for it. Yes, I suppose the xxpc chunks might perhaps be
>> indexed. In any case, it currently won't play correctly in FFplay. I'll
>> try to limit my messages (I have said it before, but I'm fully aware of
>> this problem).
>>
>> Mats
>>
>> _______________________________________________
>>
>
> The xxpc chunks are indexed alright. I checked the index in the file. Why
> FFplay will barf on it is another question.


It's probably simply not aware that such index chunks are valid. Check
libavformat/avidec.c and add relevant code to index parsing (on
read_header) and index usage (on seek) there.

Ronald