On Sat, Mar 29, 2025 at 4:26 PM Timo Rothenpieler <t...@rothenpieler.org> wrote: > > On 29.03.2025 22:17, Cameron Gutman wrote: > > On Sat, Mar 29, 2025 at 4:02 PM Timo Rothenpieler <t...@rothenpieler.org> > > wrote: > >> > >> On 29.03.2025 21:58, Cameron Gutman wrote: > >>> Some scenarios (such as game streaming or videoconferencing) may use CBR > >>> to strictly cap the maximum encoded bitrate, but they don't mind the > >>> bitrate falling below the target if the encoder doesn't need the > >>> additional headroom. > >> > >> But why aren't they using vbr with a maxrate then? > >> I didn't add this conditionally since when in CBR mode, you actually > >> really want a constant bitrate. > >> If you're okay with it dropping lower, why not use another mode with a > >> maxrate set? > >> > > > > As I understand it, the rate control behavior of CBR without filler is > > different from > > just using VBR, particularly for low latency applications. Nvidia > > recommends use > > of CBR [0] (with or without filler depending on application needs [1]) > > rather than > > using VBR for low latency applications. > > > > Also FWIW, we don't set enableFillerDataInsertion for CBR on H.264 and HEVC, > > so those will dip below the target bitrate in CBR mode while AV1 will not. > > We probably should really. In the past outputBufferingPeriodSEI > controlled this in some weird way. > > The expectation of CBR by default should be to be actually constant no > matter what. > > I just don't know what actual role the buffering period SEI plays this > day, with the new option now existing. > > If you like you can add the same logic for that flag as well. > > I'd also prefer this to be called strict_cbr or cbr_padding or > something, to make it obvious what it relates to.
To ensure I understand, you want the following: 1. Rename the filler_data option in this patch to strict_cbr (keeping the default value of 1) 2. Change H.264 and HEVC to set enableFillerDataInsertion for CBR by default and add strict_cbr option to those too 3. Don't set outputBufferingPeriodSEI = 1 unless filler data is also enabled Is that correct? > > > [0]: > > https://docs.nvidia.com/video-technologies/video-codec-sdk/12.1/nvenc-video-encoder-api-prog-guide/index.html#recommended-nvenc-settings__table-nvenc-settings > > [1]: > > https://docs.nvidia.com/video-technologies/video-codec-sdk/12.1/nvenc-video-encoder-api-prog-guide/index.html#rate-control > > > >>> Allow users to opt-out of filler data in CBR mode for those usecases > >>> where it is unwanted. > >>> > >>> Signed-off-by: Cameron Gutman <aicomman...@gmail.com> > >>> --- > >>> v2: Rebased to resolve conflicts against master > >>> --- > >>> libavcodec/nvenc.c | 2 +- > >>> libavcodec/nvenc.h | 1 + > >>> libavcodec/nvenc_av1.c | 2 ++ > >>> 3 files changed, 4 insertions(+), 1 deletion(-) > >>> > >>> diff --git a/libavcodec/nvenc.c b/libavcodec/nvenc.c > >>> index 0f5e772b3e..0f2336b0ec 100644 > >>> --- a/libavcodec/nvenc.c > >>> +++ b/libavcodec/nvenc.c > >>> @@ -1624,7 +1624,7 @@ static av_cold int > >>> nvenc_setup_av1_config(AVCodecContext *avctx) > >>> > >>> av1->idrPeriod = cc->gopLength; > >>> > >>> - if (IS_CBR(cc->rcParams.rateControlMode)) { > >>> + if (ctx->filler_data && IS_CBR(cc->rcParams.rateControlMode)) { > >>> av1->enableBitstreamPadding = 1; > >>> } > >>> > >>> diff --git a/libavcodec/nvenc.h b/libavcodec/nvenc.h > >>> index e035e123c6..3431457422 100644 > >>> --- a/libavcodec/nvenc.h > >>> +++ b/libavcodec/nvenc.h > >>> @@ -309,6 +309,7 @@ typedef struct NvencContext > >>> int unidir_b; > >>> int split_encode_mode; > >>> int mdm, cll; > >>> + int filler_data; > >>> } NvencContext; > >>> > >>> int ff_nvenc_encode_init(AVCodecContext *avctx); > >>> diff --git a/libavcodec/nvenc_av1.c b/libavcodec/nvenc_av1.c > >>> index 01626113ab..c00817af7b 100644 > >>> --- a/libavcodec/nvenc_av1.c > >>> +++ b/libavcodec/nvenc_av1.c > >>> @@ -156,6 +156,8 @@ static const AVOption options[] = { > >>> > >>> OFFSET(extra_sei), AV_OPT_TYPE_BOOL, { .i64 = 1 }, 0, 1, VE }, > >>> { "a53cc", "Use A53 Closed Captions (if available)", > >>> OFFSET(a53_cc), AV_OPT_TYPE_BOOL, { .i64 = 1 }, 0, 1, VE }, > >>> { "s12m_tc", "Use timecode (if available)", > >>> OFFSET(s12m_tc), AV_OPT_TYPE_BOOL, { .i64 = 1 }, 0, 1, VE }, > >>> + { "filler_data", "Use filler data to ensure CBR bitrate is strictly > >>> adhered to", > >>> + > >>> OFFSET(filler_data), AV_OPT_TYPE_BOOL, { .i64 = 1 }, 0, 1, VE }, > >>> #ifdef NVENC_HAVE_H264_AND_AV1_TEMPORAL_FILTER > >>> { "tf_level", "Specifies the strength of the temporal > >>> filtering", > >>> > >>> OFFSET(tf_level), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, INT_MAX, VE, > >>> .unit = "tf_level" }, > >> > >> _______________________________________________ > >> 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".
