[FFmpeg-devel] [PATCH 2/2] lavc/vaapi_decode: recreate hw_frames_ctx without destroy va_context
Yan Wang
yan.wang at linux.intel.com
Mon Jul 8 09:45:53 EEST 2019
On 7/7/2019 9:49 PM, Fu, Linjie wrote:
>> -----Original Message-----
>> From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On Behalf
>> Of Mark Thompson
>> Sent: Sunday, July 7, 2019 19:51
>> To: ffmpeg-devel at ffmpeg.org
>> Subject: Re: [FFmpeg-devel] [PATCH 2/2] lavc/vaapi_decode: recreate
>> hw_frames_ctx without destroy va_context
>>
>> On 07/07/2019 17:38, Linjie Fu wrote:
>>> VP9 allows resolution changes per frame. Currently in VAAPI, resolution
>>> changes leads to va context destroy and reinit.
>> Which is correct - it needs to remake the context because the old one is for
>> the wrong resolution.
> It seems that we don't need to remake context, remaking the surface is enough
> for resolution changing.
> Currently in libva, surface is able to be recreated separately without remaking context.
> And this way is used in libyami to cope with resolution changing cases.
>
>>> This will cause
>>> reference frame surface lost and produce garbage.
>> This isn't right - the reference frame surfaces aren't lost. See
>> VP9Context.s.refs[], which holds references to the frames (including their
>> hardware frame contexts) until the stream indicates that they can be
>> discarded by overwriting their reference frame slots.
> I'm not quite sure about this, at least the result shows they are not used correctly
> in current way.
> Will look deeper into it.
In vaapi_vp9_start_frame() of libavcodec/vaapi_vp9.c, it only passes
VASurfaceID into pic_param.reference_frames[i].
But when destroy va_context, the surface/render target based on this
VASurfaceID has been destroyed.
So the new va_context cannot find the corresponding surface based on
this surface ID.
IMHO, one possible solution is to create one the VA surfaces including
VP9Context.s.refs[] data which is AVFrame in fact and pass them into
libva when re-creating new va_context.
Thanks.
Yan Wang
>
>>> As libva allows re-create surface separately without changing the
>>> context, this issue could be handled by only recreating hw_frames_ctx.
>>>
>>> Could be verified by:
>>> ffmpeg -hwaccel vaapi -hwaccel_device /dev/dri/renderD128 -i
>>> ./resolutions.ivf
>>> -pix_fmt p010le -f rawvideo -vframes 20 -y vaapi.yuv
>>>
>>> Signed-off-by: Linjie Fu <linjie.fu at intel.com>
>>> ---
>>> libavcodec/decode.c | 8 ++++----
>>> libavcodec/vaapi_decode.c | 40 ++++++++++++++++++++++----------------
>> --
>>> 2 files changed, 26 insertions(+), 22 deletions(-)
>>>
>>> diff --git a/libavcodec/decode.c b/libavcodec/decode.c
>>> index 0863b82..a81b857 100644
>>> --- a/libavcodec/decode.c
>>> +++ b/libavcodec/decode.c
>>> @@ -1254,7 +1254,6 @@ int
>> ff_decode_get_hw_frames_ctx(AVCodecContext *avctx,
>>> frames_ctx = (AVHWFramesContext*)avctx->hw_frames_ctx->data;
>>>
>>> -
>>> if (frames_ctx->initial_pool_size) {
>>> // We guarantee 4 base work surfaces. The function above guarantees
>> 1
>>> // (the absolute minimum), so add the missing count.
>>> @@ -1333,7 +1332,7 @@ static int hwaccel_init(AVCodecContext *avctx,
>>> return AVERROR_PATCHWELCOME;
>>> }
>>>
>>> - if (hwaccel->priv_data_size) {
>>> + if (hwaccel->priv_data_size && !avctx->internal->hwaccel_priv_data) {
>>> avctx->internal->hwaccel_priv_data =
>>> av_mallocz(hwaccel->priv_data_size);
>>> if (!avctx->internal->hwaccel_priv_data)
>>> @@ -1397,8 +1396,9 @@ int ff_get_format(AVCodecContext *avctx, const
>> enum AVPixelFormat *fmt)
>>> for (;;) {
>>> // Remove the previous hwaccel, if there was one.
>>> - hwaccel_uninit(avctx);
>>> -
>>> + // VAAPI allows reinit hw_frames_ctx only
>>> + if (choices[0] != AV_PIX_FMT_VAAPI_VLD)
>> Including codec-specific conditions in the generic code suggests that
>> something very shady is going on.
> Yes, will try to avoid this.
>
>>> + hwaccel_uninit(avctx);> user_choice = avctx-
>>> get_format(avctx, choices);
>>> if (user_choice == AV_PIX_FMT_NONE) {
>>> // Explicitly chose nothing, give up.
>>> diff --git a/libavcodec/vaapi_decode.c b/libavcodec/vaapi_decode.c
>>> index 69512e1..13f0cf0 100644
>>> --- a/libavcodec/vaapi_decode.c
>>> +++ b/libavcodec/vaapi_decode.c
>>> @@ -613,8 +613,10 @@ int ff_vaapi_decode_init(AVCodecContext *avctx)
>>> VAStatus vas;
>>> int err;
>>>
>>> - ctx->va_config = VA_INVALID_ID;
>>> - ctx->va_context = VA_INVALID_ID;
>>> + if (!ctx->va_config && !ctx->va_context){
>>> + ctx->va_config = VA_INVALID_ID;
>>> + ctx->va_context = VA_INVALID_ID;
>>> + }
>>>
>>> #if FF_API_STRUCT_VAAPI_CONTEXT
>>> if (avctx->hwaccel_context) {
>>> @@ -642,7 +644,6 @@ int ff_vaapi_decode_init(AVCodecContext *avctx)
>>> // present, so set it here to avoid the behaviour changing.
>>> ctx->hwctx->driver_quirks =
>>> AV_VAAPI_DRIVER_QUIRK_RENDER_PARAM_BUFFERS;
>>> -
>>> }
>>> #endif
>>>
>>> @@ -655,7 +656,8 @@ int ff_vaapi_decode_init(AVCodecContext *avctx)
>>> "context: %#x/%#x.\n", ctx->va_config, ctx->va_context);
>>> } else {
>>> #endif
>>> -
>>> + // Get a new hw_frames_ctx even if there is already one
>>> + // recreate surface without reconstuct va_context
>>> err = ff_decode_get_hw_frames_ctx(avctx,
>> AV_HWDEVICE_TYPE_VAAPI);
>>> if (err < 0)
>>> goto fail;
>>> @@ -670,21 +672,23 @@ int ff_vaapi_decode_init(AVCodecContext *avctx)
>>> if (err)
>>> goto fail;
>>>
>>> - vas = vaCreateContext(ctx->hwctx->display, ctx->va_config,
>>> - avctx->coded_width, avctx->coded_height,
>>> - VA_PROGRESSIVE,
>>> - ctx->hwfc->surface_ids,
>>> - ctx->hwfc->nb_surfaces,
>>> - &ctx->va_context);
>>> - if (vas != VA_STATUS_SUCCESS) {
>>> - av_log(avctx, AV_LOG_ERROR, "Failed to create decode "
>>> - "context: %d (%s).\n", vas, vaErrorStr(vas));
>>> - err = AVERROR(EIO);
>>> - goto fail;
>>> - }
>>> + if (ctx->va_context == VA_INVALID_ID) {
>>> + vas = vaCreateContext(ctx->hwctx->display, ctx->va_config,
>>> + avctx->coded_width, avctx->coded_height,
>>> + VA_PROGRESSIVE,
>>> + ctx->hwfc->surface_ids,
>>> + ctx->hwfc->nb_surfaces,
>>> + &ctx->va_context);
>>> + if (vas != VA_STATUS_SUCCESS) {
>>> + av_log(avctx, AV_LOG_ERROR, "Failed to create decode "
>>> + "context: %d (%s).\n", vas, vaErrorStr(vas));
>>> + err = AVERROR(EIO);
>>> + goto fail;
>>> + }
>>>
>>> - av_log(avctx, AV_LOG_DEBUG, "Decode context initialised: "
>>> - "%#x/%#x.\n", ctx->va_config, ctx->va_context);
>>> + av_log(avctx, AV_LOG_DEBUG, "Decode context initialised: "
>>> + "%#x/%#x.\n", ctx->va_config, ctx->va_context);
>>> + }
>> If I'm reading this correctly, this changes to only creating one context ever
>> even when the resolution changes.
>>
>> How can that work if the resolution increases? For example you start
>> decoding at 1280x720 and create a context for that, then the resolution
>> changes to 3840x2160 and it tries to decode using the 1280x720 context.
>>
> Recreating hw_frame_ctx can cope with this.
> Verified in one case with resolution increasing:
> Resolution changes from 495x168 -> 328 x 307 -> 395 x376, the pipeline works
> and the output image is good.
As my understanding, you decoding output should be 495x168 always for
every frame. Right?
When the resolution of the decoded frame is different with the first
frame, the scaling is fired.
The scaling should come from media driver VP pipeline because ffmpeg use
vaGetImage() to get decoded frame.
This is dependent on ffmpeg requirement. If ffmpeg hopes to get original
decoded frame, this behavior should be changed.
Thanks.
Yan Wang
> It's not increasing on both width and height, but as long as one of them increases,
> current pipeline will be broken ff we don’t reinit the context(or just don't recreate
> hw_frame_ctx).
> (also did experiment as a contrast that we use the same context without recreate
> hw_frame_ctx, the pipeline will be blocked when mapping surface in resolution increase)
>
> ffmpeg -hwaccel vaapi -hwaccel_device /dev/dri/renderD128 -v verbose -i ./test3232.ivf
> -pix_fmt p010le -f rawvideo -vf scale=w=416:h=168 -vframes 10 -y md5.yuv
>
> log is attached.
>
> Thanks.
>
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