[FFmpeg-devel] [PATCH] AVHWAccel infrastructure v2 (take 3)

[Gwenole Beauchesne]

Hi,

On Sun, 15 Nov 2009, Michael Niedermayer wrote:

> On Fri, Nov 13, 2009 at 04:50:11PM +0100, Gwenole Beauchesne wrote:
>> On Mon, 9 Nov 2009, Michael Niedermayer wrote:
>>
>>> [...]
>>>> @@ -2526,6 +2527,14 @@ typedef struct AVCodecContext {
>>>>       * - decoding: Set by libavcodec
>>>>       */
>>>>       enum AVChromaLocation chroma_sample_location;
>>>> +
>>>> +    /**
>>>> +     * Hardware accelerator configuration attributes.
>>>> +     * The array is terminated by HWACCEL_ATTR_NONE.
>>>> +     * - encoding: unused
>>>> +     * - decoding: Set by user
>>>> +     */
>>>> +    const uintptr_t *hwaccel_attrs;
>>>>  } AVCodecContext;
>>>>
>>>>  /**
>>>
>>> uintptr_t is an optional type in C
>>> and i really have a bad feeling about using it in public API, i bet this
>>> will break several compilers
>>>
>>> and this way of passing information/attributes is very odd and there is
>>> no support in AVOptions to deal with that
>>> so i really think a int someflags would be better
>>
>> Do you mean I should use AVOptions directly + add an FF_OPT_TYPE_POINTER?
>> The problem is I don't see any codec using av_get_*() so I don't think that
>> was what you meant or is there another API to access AVOptions?
>
>
> i mean
>
> +   int my_flags;
> } AVCodecContext;

In the new model I wanted to use, hwaccel_context was to be solely 
maintained by libavcodec. However, it still needed a way to get some 
hwaccel context initialized by the user-application. e.g. a VADisplay 
(void *), an LPDIRECTXVIDEODECODER, etc.

I felt interesting to pass this information through hwaccel attrs along 
with other int attributes.

We might be able to solve this by:
- making that user-provided hwaccel context stick to hwaccel_context
- move what we currently know as hwaccel_context data to an 
hwaccel_context_private?

WDYT?

Or we could have ff_init_hwaccel() call some AVCodecContext.get_hwaccel() 
function that is user-implemented as follows:

/**
  * @param[in]  avctx the codec context
  * @param[in]  codec_id the codec
  * @param[out] hwaccel_context the hardware accelerator dependent context
  * @return the hardware accelerator ID, or HWACCEL_ID_NONE if none is suitable
  */
enum AVHWAccelID get_hwaccel(AVCodecContext *avctx, enum CodecID codec_id, void **hwaccel_context);

and declare AVCodecContext.hwaccel_context maintained by libavcodec for v2
?