On Mon, Jan 9, 2023 at 10:11 PM Mark Thompson <s...@jkqxz.net> wrote: > > On 09/01/2023 07:37, David Rosca wrote: > > On Mon, Jan 9, 2023 at 3:22 AM Xiang, Haihao <haihao.xi...@intel.com> wrote: > >> > >> On Do, 2022-12-29 at 22:20 +0100, David Rosca wrote: > >>> --- > >>> libavcodec/vaapi_encode_h264.c | 2 +- > >>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>> > >>> diff --git a/libavcodec/vaapi_encode_h264.c > >>> b/libavcodec/vaapi_encode_h264.c > >>> index dd17be2..d6926c4 100644 > >>> --- a/libavcodec/vaapi_encode_h264.c > >>> +++ b/libavcodec/vaapi_encode_h264.c > >>> @@ -350,7 +350,7 @@ static int > >>> vaapi_encode_h264_init_sequence_params(AVCodecContext *avctx) > >>> sps->chroma_format_idc = 1; > >>> > >>> sps->log2_max_frame_num_minus4 = 4; > >>> - sps->pic_order_cnt_type = 0; > >>> + sps->pic_order_cnt_type = ctx->max_b_depth ? 0 : 2; > >> > >> > >> pic_order_cnt_type (0) should work for ctx->max_b_depth == 0. If 2 is > >> preferred > >> for your vaapi driver, it would be better to query the capability from the > >> driver, like as what commit 9f02e033875185409c861846f209b04a3be339d2 did. > > > > It's not about an encoder, but rather about decoder. Some decoders > > (namely the Snapdragon HW decoder) > > will buffer frames when pic_order_cnt_type == 0 (in case the frames > > will be reordered?) which results > > in undesired increased latency. Setting pic_order_cnt_type to 2 will > > fix this problem, and it is also what > > libx264 does [0]. > > Has that decoder bug been reported to the vendor so that they can fix it?
I haven't and I'm not sure where I would check if it was already reported by someone else. I wasn't even sure it's a bug since all encoders I have tried so far (x264, nvenc, amf) will output pic_order_cnt_type=2 when configured for low latency encoding. > > The decoder should be reading the stream buffering from > max_num_reorder_frames in the VUI parameters, which is set at as expected > <http://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavcodec/vaapi_encode_h264.c;h=dd17be2190ab07331ed69cf830b8cea2584ad353;hb=HEAD#l478>. > > The change to using POC type 2 is not unreasonable to save a few bits, but to > do it you will also need to fix all of the POC values to actually match the > type 2 behaviour (the current type 0 setup steps by 1 on frames because > interlacing is not supported, but type 2 always steps by 2 - see ยง8.2.1.3). > > - Mark > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > To unsubscribe, visit link above, or email > ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
