[FFmpeg-devel] [PATCH] avcodec/nvenc: Use CBR filler data consistently across codecs

[Kieran Kunhya]

On Sun, Mar 30, 2025 at 12:04 AM Cameron Gutman <aicommander at gmail.com> wrote:
>
> Previously, AV1 used filler data with CBR by default while H.264
> and HEVC did not. Make this consistent by using filler data in
> CBR mode across all codecs.
>
> Since there are valid reasons to use CBR with or without filler,
> also add a cbr_padding option to allow users to opt out.
>
> Signed-off-by: Cameron Gutman <aicommander at gmail.com>
> ---
>  libavcodec/nvenc.c      | 16 +++++++++++++---
>  libavcodec/nvenc.h      |  2 ++
>  libavcodec/nvenc_av1.c  |  2 ++
>  libavcodec/nvenc_h264.c |  4 ++++
>  libavcodec/nvenc_hevc.c |  4 ++++
>  5 files changed, 25 insertions(+), 3 deletions(-)
>
> diff --git a/libavcodec/nvenc.c b/libavcodec/nvenc.c
> index 0f5e772b3e..41a4dc55f4 100644
> --- a/libavcodec/nvenc.c
> +++ b/libavcodec/nvenc.c
> @@ -1304,7 +1304,12 @@ static av_cold int nvenc_setup_h264_config(AVCodecContext *avctx)
>      h264->idrPeriod = cc->gopLength;
>
>      if (IS_CBR(cc->rcParams.rateControlMode)) {
> -        h264->outputBufferingPeriodSEI = 1;
> +        /* Older SDKs use outputBufferingPeriodSEI to control filler data */
> +        h264->outputBufferingPeriodSEI = ctx->cbr_padding;
> +
> +#ifdef NVENC_HAVE_FILLER_DATA
> +        h264->enableFillerDataInsertion = ctx->cbr_padding;
> +#endif
>      }
>
>      h264->outputPictureTimingSEI = 1;
> @@ -1503,7 +1508,12 @@ static av_cold int nvenc_setup_hevc_config(AVCodecContext *avctx)
>      hevc->idrPeriod = cc->gopLength;
>
>      if (IS_CBR(cc->rcParams.rateControlMode)) {
> -        hevc->outputBufferingPeriodSEI = 1;
> +        /* Older SDKs use outputBufferingPeriodSEI to control filler data */
> +        hevc->outputBufferingPeriodSEI = ctx->cbr_padding;
> +
> +#ifdef NVENC_HAVE_FILLER_DATA
> +        hevc->enableFillerDataInsertion = ctx->cbr_padding;
> +#endif
>      }
>
>      hevc->outputPictureTimingSEI = 1;
> @@ -1625,7 +1635,7 @@ static av_cold int nvenc_setup_av1_config(AVCodecContext *avctx)
>      av1->idrPeriod = cc->gopLength;
>
>      if (IS_CBR(cc->rcParams.rateControlMode)) {
> -        av1->enableBitstreamPadding = 1;
> +        av1->enableBitstreamPadding = ctx->cbr_padding;
>      }
>
>      if (ctx->tile_cols >= 0)
> diff --git a/libavcodec/nvenc.h b/libavcodec/nvenc.h
> index e035e123c6..4b12846ed7 100644
> --- a/libavcodec/nvenc.h
> +++ b/libavcodec/nvenc.h
> @@ -61,6 +61,7 @@ typedef void ID3D11Device;
>  #define NVENC_HAVE_MULTIPLE_REF_FRAMES
>  #define NVENC_HAVE_CUSTREAM_PTR
>  #define NVENC_HAVE_GETLASTERRORSTRING
> +#define NVENC_HAVE_FILLER_DATA
>  #endif
>
>  // SDK 10.0 compile time feature checks
> @@ -309,6 +310,7 @@ typedef struct NvencContext
>      int unidir_b;
>      int split_encode_mode;
>      int mdm, cll;
> +    int cbr_padding;
>  } NvencContext;
>
>  int ff_nvenc_encode_init(AVCodecContext *avctx);
> diff --git a/libavcodec/nvenc_av1.c b/libavcodec/nvenc_av1.c
> index 01626113ab..b1b95672f2 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 },
> +    { "cbr_padding",  "Pad the bitstream to ensure bitrate does not drop below the target in CBR mode",
> +                                                            OFFSET(cbr_padding),  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" },
> diff --git a/libavcodec/nvenc_h264.c b/libavcodec/nvenc_h264.c
> index 21d25d643a..4845d0422d 100644
> --- a/libavcodec/nvenc_h264.c
> +++ b/libavcodec/nvenc_h264.c
> @@ -231,6 +231,10 @@ static const AVOption options[] = {
>                                                              OFFSET(max_slice_size), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, VE },
>      { "constrained-encoding", "Enable constrainedFrame encoding where each slice in the constrained picture is independent of other slices",
>                                                              OFFSET(constrained_encoding), AV_OPT_TYPE_BOOL,  { .i64 = 0 }, 0, 1, VE },
> +#ifdef NVENC_HAVE_FILLER_DATA
> +    { "cbr_padding",  "Pad the bitstream to ensure bitrate does not drop below the target in CBR mode",
> +                                                            OFFSET(cbr_padding),  AV_OPT_TYPE_BOOL,  { .i64 = 1 }, 0, 1, VE },
> +#endif
>  #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" },
> diff --git a/libavcodec/nvenc_hevc.c b/libavcodec/nvenc_hevc.c
> index c74eca9bb3..8648f4f3a9 100644
> --- a/libavcodec/nvenc_hevc.c
> +++ b/libavcodec/nvenc_hevc.c
> @@ -206,6 +206,10 @@ static const AVOption options[] = {
>                                                              OFFSET(max_slice_size), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, VE },
>      { "constrained-encoding", "Enable constrainedFrame encoding where each slice in the constrained picture is independent of other slices",
>                                                              OFFSET(constrained_encoding), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, VE },
> +#ifdef NVENC_HAVE_FILLER_DATA
> +    { "cbr_padding",  "Pad the bitstream to ensure bitrate does not drop below the target in CBR mode",
> +                                                            OFFSET(cbr_padding),  AV_OPT_TYPE_BOOL,  { .i64 = 1 }, 0, 1, VE },
> +#endif
>  #ifdef NVENC_HAVE_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" },
> --
> 2.49.0


This should be off by default in FFmpeg. We don't do this in any other encoder.

Kieran