[FFmpeg-devel] [PATCH] libavcodec/vp9: Fix VP9 dynamic resolution changing decoding on VAAPI.

Yan Wang yan.wang at linux.intel.com
Fri May 31 05:58:47 EEST 2019


On 5/30/2019 7:39 AM, Mark Thompson wrote:
> On 28/05/2019 08:46, Yan Wang wrote:
>> On 5/28/2019 3:16 PM, Hendrik Leppkes wrote:
>>> On Tue, May 28, 2019 at 8:57 AM Yan Wang <yan.wang at linux.intel.com> wrote:
>>>> When the format change, the VAAPI context cannot be destroyed.
>>>> Otherwise, the reference frame surface will lost.
>>>>
>>>> Signed-off-by: Yan Wang <yan.wang at linux.intel.com>
>>>> ---
>>>>    libavcodec/decode.c | 6 ++++++
>>>>    1 file changed, 6 insertions(+)
>>>>
>>>> diff --git a/libavcodec/decode.c b/libavcodec/decode.c
>>>> index 6c31166ec2..3eda1dc42c 100644
>>>> --- a/libavcodec/decode.c
>>>> +++ b/libavcodec/decode.c
>>>> @@ -1397,7 +1397,9 @@ int ff_get_format(AVCodecContext *avctx, const enum AVPixelFormat *fmt)
>>>>
>>>>        for (;;) {
>>>>            // Remove the previous hwaccel, if there was one.
>>>> +#if !CONFIG_VP9_VAAPI_HWACCEL
>>>>            hwaccel_uninit(avctx);
>>>> +#endif
>>>>
>>>>            user_choice = avctx->get_format(avctx, choices);
>>>>            if (user_choice == AV_PIX_FMT_NONE) {
>>>> @@ -1479,7 +1481,11 @@ int ff_get_format(AVCodecContext *avctx, const enum AVPixelFormat *fmt)
>>>>                       "missing configuration.\n", desc->name);
>>>>                goto try_again;
>>>>            }
>>>> +#if CONFIG_VP9_VAAPI_HWACCEL
>>>> +        if (hw_config->hwaccel && !avctx->hwaccel) {
>>>> +#else
>>>>            if (hw_config->hwaccel) {
>>>> +#endif
>>>>                av_log(avctx, AV_LOG_DEBUG, "Format %s requires hwaccel "
>>>>                       "initialisation.\n", desc->name);
>>>>                err = hwaccel_init(avctx, hw_config);
>>>> -- 
>>>> 2.17.2
>>>>
>>> This change feels just wrong. First of all, preprocessors are
>>> absolutely the wrong way to go about this.
>> Sorry for this. I am new guy for ffmpeg development. What way should be
>>
>> better? I can refine it.
>>
>>> Secondly, if the frames need to change size, or surface format, then
>>> this absolutely needs to be called, doesn't it?
>> Based on VP9 spec, the frame resolution can be changed per frame. But current
>>
>> frame will need refer to previous frame still. So if destroy the VAAPI context, it
>>
>> will cause reference frame surface in VAAPI driver lost.
>>
>> In fact, this patch is for the issue:
>>
>> https://github.com/intel/media-driver/issues/629
>>
>> its 2nd frame (128x128) will refer to the 1st frame (256x256).
> Can you explain exactly what is going wrong here?  The surface is definitely still present - the reference frame list entry holds a reference to it.

IMHO,

for one VP9 clips with dynamic resolution changing which is legal based 
on VP9 spec.

After the 1st frame (256x256) is decoded with vaapi-hw acceleration, 
ffmpeg will parse and decode the frame header of the 2nd frame (128x128).

It will call update_size() when ffmpeg finds the resolution is changed 
and destroy/recreate vaapi-hw context which will also destroy and 
release the previous decoded 1st frame (256x256) saved in driver. The 
saved 1st frame surface should be as reference frame normally.

So when ffmpeg ask vaapi-hw to decode the 2nd frame, it cannot find the 
the 1st frame surface as reference frame and has to use dummy reference 
frame although the reference frame index is right.

I am newbie for ffmpeg code. I am studying ffmpeg related code and hope 
to compare libvpx path for looking for a better solution.

Thanks.

Yan Wang

>
> - Mark
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".


More information about the ffmpeg-devel mailing list