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frontends/va: ignore incoming frame_num from VA picture parameters

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The Gallium pipe video "frame_num" variable is internally used as a
counter of elapsed reference frames since the last IDR. The incoming
frame_num field from VA picture parameters is not equivalent; the VA
value may wrap to zero prematurely, as it is a 16-bit struct field with
a documented max value of 2^(log2_max_frame_num_minus4 + 4)-1.

This change improves "infinite GOP" single-client live streaming, where
it is reasonable for the server to desire an endless series of P-frames
without IDR. Without this change, it is difficult/impossible for an
application to encode a P- or B-frame after the VA frame_num field wraps
around to zero, depending on the backend encoder implementation.

This change has no effect on existing applications that always signal an
IDR frame and reset the VA frame_num to zero before it wraps around. For
example, the FFmpeg vaapi encoder ignores the VA documentation and sends
an un-wrapped VA frame_num, which results in identical computation of
the internal frame_num (as long as each GOP is less than 65536 frames).

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5768

Reviewed-by: Thong Thai <thong.thai@amd.com>

patch revision 3: correctly avoid incrementing frame_num when the encoded
frame is not a reference, per h264 spec and ffmpeg behavior

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14332>
This commit is contained in:
Henry Goffin 2021-12-29 09:20:30 +00:00 • committed by Marge Bot
parent d28b6b6856
commit c8f644ec44
2 changed files with 5 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
src/gallium/frontends/va/picture.c
View file

@ -813,6 +813,8 @@ vlVaEndPicture(VADriverContextP ctx, VAContextID context_id)
context->first_single_submitted = false;
surf->force_flushed = true;
}
if (!context->desc.h264enc.not_referenced)
context->desc.h264enc.frame_num++;
} else if (context->decoder->entrypoint == PIPE_VIDEO_ENTRYPOINT_ENCODE &&
u_reduce_video_profile(context->templat.profile) == PIPE_VIDEO_FORMAT_HEVC)
context->desc.h265enc.frame_num++;

5
src/gallium/frontends/va/picture_h264_enc.c
View file

@ -36,7 +36,8 @@ vlVaHandleVAEncPictureParameterBufferTypeH264(vlVaDriver *drv, vlVaContext *cont
vlVaBuffer *coded_buf;
h264 = buf->data;
context->desc.h264enc.frame_num = h264->frame_num;
if (h264->pic_fields.bits.idr_pic_flag == 1)
context->desc.h264enc.frame_num = 0;
context->desc.h264enc.not_referenced = !h264->pic_fields.bits.reference_pic_flag;
context->desc.h264enc.pic_order_cnt = h264->CurrPic.TopFieldOrderCnt;
if (context->desc.h264enc.gop_cnt == 0)
@ -54,7 +55,7 @@ vlVaHandleVAEncPictureParameterBufferTypeH264(vlVaDriver *drv, vlVaContext *cont
_mesa_hash_table_insert(context->desc.h264enc.frame_idx,
UINT_TO_PTR(h264->CurrPic.picture_id + 1),
UINT_TO_PTR(h264->frame_num));
UINT_TO_PTR(context->desc.h264enc.frame_num));
if (h264->pic_fields.bits.idr_pic_flag == 1)
context->desc.h264enc.picture_type = PIPE_H2645_ENC_PICTURE_TYPE_IDR;