Re: [FFmpeg-devel] [PATCH v2] avcodec/av1dec: convert to receive_frame()

[James Almer <jamrial@gmail.com>]

On 5/20/2023 2:07 PM, Andreas Rheinhardt wrote:
> James Almer:
>> On 5/20/2023 1:59 PM, Andreas Rheinhardt wrote:
>>> James Almer:
>>>> On 5/20/2023 1:12 PM, Anton Khirnov wrote:
>>>>> Quoting James Almer (2023-05-20 03:50:57)
>>>>>> Signed-off-by: James Almer <jamrial@gmail.com>
>>>>>> ---
>>>>>>     libavcodec/av1dec.c | 75
>>>>>> +++++++++++++++++++++++++++++++++------------
>>>>>>     libavcodec/av1dec.h |  4 +++
>>>>>>     2 files changed, 60 insertions(+), 19 deletions(-)
>>>>>
>>>>> The patch makes the code longer and introduces an evil backward goto.
>>>>> So some comment on why is this an improvement would be appropriate.
>>>>
>>>> It's an improvement because it removes the auto-inserted av1_frame_split
>>>> from the process, making the decoder handle temporal units with more
>>>> than one frame in them on its own. I can add that to the commit message.
>>>>
>>>> The extra code is inevitable because it's the decoder who now needs to
>>>> fetch the packet instead of the generic code in decode.c
>>>
>>> 1. Where is the improvement in that? What is so bad about using a BSF to
>>> preprocess packets in this way?
>>
>> Much less overhead? One less instance of CBS, less function calls, less
>> packet references generated and moved around, etc.
>>
> 
> This is AV1, not annex B H.2645.

I'm sorry, i don't understand what you're trying to say. The 
av1_frame_split bsf will split a TU into individual frames, and uses the 
CBS framework for this. It's an unnecessary overhead when the decoder 
can be made to handle this on its own by making it use the proper decode 
callback.
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