> This implements a simple reactive VBR rate control mode for single-layer
> H.264.
> The primary aim here is to avoid the problematic behaviour that the CBR rate
> controller displays on scene changes, where the QP can get pushed up by a
> large
> amount in a short period and compromise the quality of following frames to a
> very visible degree.
>
> The main idea, then, is to try to keep the HRD buffering above the target
> level
> most of the time, so that when a large frame is generated (on a scene change
> or
> when the stream complexity increases) we have plenty of slack to be able to
> encode the more difficult region without compromising quality immediately on
> the following frames. It is optimistic about the complexity of future
> frames,
> so even after generating one or more large frames on a significant change it
> will try to keep the QP at its current level until the HRD buffer bounds force
> a change to maintain the intended rate.
>
> Compared to the CBR rate controller, it keeps the quality level much more
> stable - QP does not always spike up as large frames are generated when the
> complexity of the stream increases transiently, but equally it does not reduce
> as quickly when the complexity of the stream decreases.
>
> Signed-off-by: Mark Thompson <s...@jkqxz.net>
> ---
> On 06/01/17 07:09, Xiang, Haihao wrote:
> >
> > > ...
> >
> > Could you add the above message in your commit log? I don't see the message
> > after applying this patch to my local branch.
>
> It was more meant as a general explanation rather than a commit message. But
> yes, it should probably have something more. I've rewritten the comment in
> the code to be a bit more complete and also set it as the commit message
> above.
>
> > The expected target bitrate for VBR is (target_percentage *
> > bits_per_second),
> > e.g. for vp9
> >
> > vp9_state->target_bit_rate = vp9_state->max_bit_rate * encoder_context-
> > > brc.target_percentage[0] / 100
> >
> > we should keep the same behavior for all codecs.
>
> Hmm. I initially did do this, but decided it wasn't quite right because this
> rate controller doesn't really have a maximum bitrate - it is constrained
> only by the HRD buffering.
>
> Still, the point about keeping the behaviour consistent is probably more
> important, so I've made the simple change to multiply by the percentage. It
> might be worth considering later how the maximum bitrate should actually be
> treated here, though.
>
> Thanks,
>
> - Mark
>
>
> src/gen6_mfc.c | 10 ++--
> src/gen6_mfc_common.c | 125
> ++++++++++++++++++++++++++++++++++++++++++++++++--
> src/gen75_mfc.c | 10 ++--
> src/gen8_mfc.c | 10 ++--
> src/i965_drv_video.c | 5 +-
> 5 files changed, 140 insertions(+), 20 deletions(-)
>
> diff --git a/src/gen6_mfc.c b/src/gen6_mfc.c
> index 8077c14..1765530 100644
> --- a/src/gen6_mfc.c
> +++ b/src/gen6_mfc.c
> @@ -798,7 +798,7 @@ gen6_mfc_avc_pipeline_slice_programing(VADriverContextP
> ctx,
> int qp_mb;
>
> qp_slice = qp;
> - if (rate_control_mode == VA_RC_CBR) {
> + if (rate_control_mode != VA_RC_CQP) {
> qp =
> mfc_context->brc.qp_prime_y[encoder_context->layer.curr_frame_layer_id][slice_type];
> if (encode_state->slice_header_index[slice_index] == 0) {
> pSliceParameter->slice_qp_delta = qp -
> pPicParameter->pic_init_qp;
> @@ -816,7 +816,7 @@ gen6_mfc_avc_pipeline_slice_programing(VADriverContextP
> ctx,
> pPicParameter,
> pSliceParameter,
> encode_state, encoder_context,
> - (rate_control_mode == VA_RC_CBR), qp_slice,
> slice_batch);
> + (rate_control_mode != VA_RC_CQP), qp_slice,
> slice_batch);
>
> if ( slice_index == 0)
> intel_mfc_avc_pipeline_header_programing(ctx, encode_state,
> encoder_context, slice_batch);
> @@ -1188,7 +1188,7 @@ gen6_mfc_avc_batchbuffer_slice(VADriverContextP ctx,
> int qp_slice;
>
> qp_slice = qp;
> - if (rate_control_mode == VA_RC_CBR) {
> + if (rate_control_mode != VA_RC_CQP) {
> qp =
> mfc_context->brc.qp_prime_y[encoder_context->layer.curr_frame_layer_id][slice_type];
> if (encode_state->slice_header_index[slice_index] == 0) {
> pSliceParameter->slice_qp_delta = qp -
> pPicParameter->pic_init_qp;
> @@ -1209,7 +1209,7 @@ gen6_mfc_avc_batchbuffer_slice(VADriverContextP ctx,
> pSliceParameter,
> encode_state,
> encoder_context,
> - (rate_control_mode == VA_RC_CBR),
> + (rate_control_mode != VA_RC_CQP),
> qp_slice,
> slice_batch);
>
> @@ -1368,7 +1368,7 @@ gen6_mfc_avc_encode_picture(VADriverContextP ctx,
> /*Programing bcs pipeline*/
> gen6_mfc_avc_pipeline_programing(ctx, encode_state,
> encoder_context);> > //filling the pipeline
> gen6_mfc_run(ctx, encode_state, encoder_context);
> - if (rate_control_mode == VA_RC_CBR /*|| rate_control_mode ==
> VA_RC_VBR*/) {
> + if (rate_control_mode == VA_RC_CBR || rate_control_mode ==
> VA_RC_VBR) {
> gen6_mfc_stop(ctx, encode_state, encoder_context,
> ¤t_frame_bits_size);
> sts = intel_mfc_brc_postpack(encode_state, encoder_context,
> current_frame_bits_size);
> if (sts == BRC_NO_HRD_VIOLATION) {
> diff --git a/src/gen6_mfc_common.c b/src/gen6_mfc_common.c
> index fbedc94..9e0bb55 100644
> --- a/src/gen6_mfc_common.c
> +++ b/src/gen6_mfc_common.c
> @@ -127,6 +127,9 @@ static void intel_mfc_brc_init(struct encode_state
> *encode_state,
> ((double)encoder_context->brc.framerate[i - 1].num /
> (double)encoder_context->brc.framerate[i - 1].den);
> }
>
> + if (mfc_context->brc.mode == VA_RC_VBR &&
> encoder_context->brc.target_percentage[i])
> + bitrate = bitrate * encoder_context->brc.target_percentage[i] /
> 100;
> +
> if (i == encoder_context->layer.num_layers - 1)
> factor = 1.0;
> else {
> @@ -219,9 +222,9 @@ int intel_mfc_update_hrd(struct encode_state
> *encode_state,
> return BRC_NO_HRD_VIOLATION;
> }
>
> -int intel_mfc_brc_postpack(struct encode_state *encode_state,
> - struct intel_encoder_context *encoder_context,
> - int frame_bits)
> +static int intel_mfc_brc_postpack_cbr(struct encode_state *encode_state,
> + struct intel_encoder_context
> *encoder_context,
> + int frame_bits)
> {
> struct gen6_mfc_context *mfc_context = encoder_context->mfc_context;
> gen6_brc_status sts = BRC_NO_HRD_VIOLATION;
> @@ -368,6 +371,120 @@ int intel_mfc_brc_postpack(struct encode_state
> *encode_state,
> return sts;
> }
>
> +static int intel_mfc_brc_postpack_vbr(struct encode_state *encode_state,
> + struct intel_encoder_context
> *encoder_context,
> + int frame_bits)
> +{
> + struct gen6_mfc_context *mfc_context = encoder_context->mfc_context;
> + gen6_brc_status sts;
> + VAEncSliceParameterBufferH264 *pSliceParameter =
> (VAEncSliceParameterBufferH264 *)encode_state->slice_params_ext[0]->buffer;
> + int slice_type =
> intel_avc_enc_slice_type_fixup(pSliceParameter->slice_type);
> + int *qp = mfc_context->brc.qp_prime_y[0];
> + int qp_delta, large_frame_adjustment;
> +
> + // This implements a simple reactive VBR rate control mode for
> single-layer H.264. The primary
> + // aim here is to avoid the problematic behaviour that the CBR rate
> controller displays on
> + // scene changes, where the QP can get pushed up by a large amount in a
> short period and
> + // compromise the quality of following frames to a very visible degree.
> + // The main idea, then, is to try to keep the HRD buffering above the
> target level most of the
> + // time, so that when a large frame is generated (on a scene change or
> when the stream
> + // complexity increases) we have plenty of slack to be able to encode
> the more difficult region
> + // without compromising quality immediately on the following frames.
> It is optimistic about
> + // the complexity of future frames, so even after generating one or more
> large frames on a
> + // significant change it will try to keep the QP at its current level
> until the HRD buffer
> + // bounds force a change to maintain the intended rate.
> +
> + sts = intel_mfc_update_hrd(encode_state, encoder_context, frame_bits);
> +
> + // This adjustment is applied to increase the QP by more than we
> normally would if a very
> + // large frame is encountered and we are in danger of running out of
> slack.
> + large_frame_adjustment = rint(2.0 * log(frame_bits /
> mfc_context->brc.target_frame_size[0][slice_type]));
> +
> + if (sts == BRC_UNDERFLOW) {
> + // The frame is far too big and we don't have the bits available to
> send it, so it will
> + // have to be re-encoded at a higher QP.
> + qp_delta = +2;
> + if (frame_bits > mfc_context->brc.target_frame_size[0][slice_type])
> + qp_delta += large_frame_adjustment;
> + } else if (sts == BRC_OVERFLOW) {
> + // The frame is very small and we are now overflowing the HRD
> buffer. Currently this case
> + // does not occur because we ignore overflow in VBR mode.
> + assert(0 && "Overflow in VBR mode");
> + } else if (frame_bits <=
> mfc_context->brc.target_frame_size[0][slice_type]) {
> + // The frame is smaller than the average size expected for this
> frame type.
> + if (mfc_context->hrd.current_buffer_fullness[0] >
> + (mfc_context->hrd.target_buffer_fullness[0] +
> mfc_context->hrd.buffer_size[0]) / 2.0) {
> + // We currently have lots of bits available, so decrease the QP
> slightly for the next
> + // frame.
> + qp_delta = -1;
> + } else {
> + // The HRD buffer fullness is increasing, so do nothing. (We
> may be under the target
> + // level here, but are moving in the right direction.)
> + qp_delta = 0;
> + }
> + } else {
> + // The frame is larger than the average size expected for this frame
> type.
> + if (mfc_context->hrd.current_buffer_fullness[0] >
> mfc_context->hrd.target_buffer_fullness[0]) {
> + // We are currently over the target level, so do nothing.
> + qp_delta = 0;
> + } else if (mfc_context->hrd.current_buffer_fullness[0] >
> mfc_context->hrd.target_buffer_fullness[0] / 2.0) {
> + // We are under the target level, but not critically. Increase
> the QP by one step if
> + // continuing like this would underflow soon (currently within
> one second).
> + if (mfc_context->hrd.current_buffer_fullness[0] /
> + (double)(frame_bits -
> mfc_context->brc.target_frame_size[0][slice_type] + 1) <
> + ((double)encoder_context->brc.framerate[0].num /
> (double)encoder_context->brc.framerate[0].den))
> + qp_delta = +1;
> + else
> + qp_delta = 0;
> + } else {
> + // We are a long way under the target level. Always increase
> the QP, possibly by a
> + // larger amount dependent on how big the frame we just made
> actually was.
> + qp_delta = +1 + large_frame_adjustment;
> + }
> + }
> +
> + switch (slice_type) {
> + case SLICE_TYPE_I:
> + qp[SLICE_TYPE_I] += qp_delta;
> + qp[SLICE_TYPE_P] = qp[SLICE_TYPE_I] + BRC_I_P_QP_DIFF;
> + qp[SLICE_TYPE_B] = qp[SLICE_TYPE_I] + BRC_I_B_QP_DIFF;
> + break;
> + case SLICE_TYPE_P:
> + qp[SLICE_TYPE_P] += qp_delta;
> + qp[SLICE_TYPE_I] = qp[SLICE_TYPE_P] - BRC_I_P_QP_DIFF;
> + qp[SLICE_TYPE_B] = qp[SLICE_TYPE_P] + BRC_P_B_QP_DIFF;
> + break;
> + case SLICE_TYPE_B:
> + qp[SLICE_TYPE_B] += qp_delta;
> + qp[SLICE_TYPE_I] = qp[SLICE_TYPE_B] - BRC_I_B_QP_DIFF;
> + qp[SLICE_TYPE_P] = qp[SLICE_TYPE_B] - BRC_P_B_QP_DIFF;
> + break;
> + }
> + BRC_CLIP(mfc_context->brc.qp_prime_y[0][SLICE_TYPE_I],
> (int)encoder_context->brc.min_qp, 51);
> + BRC_CLIP(mfc_context->brc.qp_prime_y[0][SLICE_TYPE_P],
> (int)encoder_context->brc.min_qp, 51);
> + BRC_CLIP(mfc_context->brc.qp_prime_y[0][SLICE_TYPE_B],
> (int)encoder_context->brc.min_qp, 51);
The lower bound is 1 when encoder_context->brc.min_qp is equal to 0.
> +
> + if (sts == BRC_UNDERFLOW && qp[slice_type] == 51)
> + sts = BRC_UNDERFLOW_WITH_MAX_QP;
> + if (sts == BRC_OVERFLOW && qp[slice_type] == encoder_context->brc.min_qp)
Same as above
> + sts = BRC_OVERFLOW_WITH_MIN_QP;
> +
> + return sts;
> +}
> +
> +int intel_mfc_brc_postpack(struct encode_state *encode_state,
> + struct intel_encoder_context *encoder_context,
> + int frame_bits)
> +{
> + switch (encoder_context->rate_control_mode) {
> + case VA_RC_CBR:
> + return intel_mfc_brc_postpack_cbr(encode_state, encoder_context,
> frame_bits);
> + case VA_RC_VBR:
> + return intel_mfc_brc_postpack_vbr(encode_state, encoder_context,
> frame_bits);
> + }
> + assert(0 && "Invalid RC mode");
> +}
> +
> static void intel_mfc_hrd_context_init(struct encode_state *encode_state,
> struct intel_encoder_context
> *encoder_context)
> {
> @@ -427,7 +544,7 @@ void intel_mfc_brc_prepare(struct encode_state
> *encode_state,
> encoder_context->codec != CODEC_H264_MVC)
> return;
>
> - if (rate_control_mode == VA_RC_CBR) {
> + if (rate_control_mode != VA_RC_CQP) {
> /*Programing bit rate control */
> if (encoder_context->brc.need_reset) {
> intel_mfc_bit_rate_control_context_init(encode_state,
> encoder_context);
> diff --git a/src/gen75_mfc.c b/src/gen75_mfc.c
> index 0fbbe76..7b76b99 100644
> --- a/src/gen75_mfc.c
> +++ b/src/gen75_mfc.c
> @@ -1174,7 +1174,7 @@
> gen75_mfc_avc_pipeline_slice_programing(VADriverContextP ctx,
> int qp_mb;
>
> qp_slice = qp;
> - if (rate_control_mode == VA_RC_CBR) {
> + if (rate_control_mode != VA_RC_CQP) {
> qp =
> mfc_context->brc.qp_prime_y[encoder_context->layer.curr_frame_layer_id][slice_type];
> if (encode_state->slice_header_index[slice_index] == 0) {
> pSliceParameter->slice_qp_delta = qp -
> pPicParameter->pic_init_qp;
> @@ -1192,7 +1192,7 @@
> gen75_mfc_avc_pipeline_slice_programing(VADriverContextP ctx,
> pPicParameter,
> pSliceParameter,
> encode_state, encoder_context,
> - (rate_control_mode == VA_RC_CBR), qp_slice,
> slice_batch);
> + (rate_control_mode != VA_RC_CQP), qp_slice,
> slice_batch);
>
> if ( slice_index == 0)
> intel_mfc_avc_pipeline_header_programing(ctx, encode_state,
> encoder_context, slice_batch);
> @@ -1521,7 +1521,7 @@ gen75_mfc_avc_batchbuffer_slice(VADriverContextP ctx,
> int qp_slice;
>
> qp_slice = qp;
> - if (rate_control_mode == VA_RC_CBR) {
> + if (rate_control_mode != VA_RC_CQP) {
> qp =
> mfc_context->brc.qp_prime_y[encoder_context->layer.curr_frame_layer_id][slice_type];
> if (encode_state->slice_header_index[slice_index] == 0) {
> pSliceParameter->slice_qp_delta = qp -
> pPicParameter->pic_init_qp;
> @@ -1540,7 +1540,7 @@ gen75_mfc_avc_batchbuffer_slice(VADriverContextP ctx,
> pSliceParameter,
> encode_state,
> encoder_context,
> - (rate_control_mode == VA_RC_CBR),
> + (rate_control_mode != VA_RC_CQP),
> qp_slice,
> slice_batch);
>
> @@ -1702,7 +1702,7 @@ gen75_mfc_avc_encode_picture(VADriverContextP ctx,
> /*Programing bcs pipeline*/
> gen75_mfc_avc_pipeline_programing(ctx, encode_state,
> encoder_context);> > //filling the pipeline
> gen75_mfc_run(ctx, encode_state, encoder_context);
> - if (rate_control_mode == VA_RC_CBR /*|| rate_control_mode ==
> VA_RC_VBR*/) {
> + if (rate_control_mode == VA_RC_CBR || rate_control_mode ==
> VA_RC_VBR) {
> gen75_mfc_stop(ctx, encode_state, encoder_context,
> ¤t_frame_bits_size);
> sts = intel_mfc_brc_postpack(encode_state, encoder_context,
> current_frame_bits_size);
> if (sts == BRC_NO_HRD_VIOLATION) {
> diff --git a/src/gen8_mfc.c b/src/gen8_mfc.c
> index 90119d7..8e68c7c 100644
> --- a/src/gen8_mfc.c
> +++ b/src/gen8_mfc.c
> @@ -1177,7 +1177,7 @@ gen8_mfc_avc_pipeline_slice_programing(VADriverContextP
> ctx,
> int qp_mb;
>
> qp_slice = qp;
> - if (rate_control_mode == VA_RC_CBR) {
> + if (rate_control_mode != VA_RC_CQP) {
> qp =
> mfc_context->brc.qp_prime_y[encoder_context->layer.curr_frame_layer_id][slice_type];
> if (encode_state->slice_header_index[slice_index] == 0) {
> pSliceParameter->slice_qp_delta = qp -
> pPicParameter->pic_init_qp;
> @@ -1195,7 +1195,7 @@ gen8_mfc_avc_pipeline_slice_programing(VADriverContextP
> ctx,
> pPicParameter,
> pSliceParameter,
> encode_state, encoder_context,
> - (rate_control_mode == VA_RC_CBR), qp_slice,
> slice_batch);
> + (rate_control_mode != VA_RC_CQP), qp_slice,
> slice_batch);
>
> if ( slice_index == 0)
> intel_mfc_avc_pipeline_header_programing(ctx, encode_state,
> encoder_context, slice_batch);
> @@ -1534,7 +1534,7 @@ gen8_mfc_avc_batchbuffer_slice(VADriverContextP ctx,
> int qp_slice;
>
> qp_slice = qp;
> - if (rate_control_mode == VA_RC_CBR) {
> + if (rate_control_mode != VA_RC_CQP) {
> qp =
> mfc_context->brc.qp_prime_y[encoder_context->layer.curr_frame_layer_id][slice_type];
> if (encode_state->slice_header_index[slice_index] == 0) {
> pSliceParameter->slice_qp_delta = qp -
> pPicParameter->pic_init_qp;
> @@ -1553,7 +1553,7 @@ gen8_mfc_avc_batchbuffer_slice(VADriverContextP ctx,
> pSliceParameter,
> encode_state,
> encoder_context,
> - (rate_control_mode == VA_RC_CBR),
> + (rate_control_mode != VA_RC_CQP),
> qp_slice,
> slice_batch);
>
> @@ -1729,7 +1729,7 @@ gen8_mfc_avc_encode_picture(VADriverContextP ctx,
> /*Programing bcs pipeline*/
> gen8_mfc_avc_pipeline_programing(ctx, encode_state,
> encoder_context);> > //filling the pipeline
> gen8_mfc_run(ctx, encode_state, encoder_context);
> - if (rate_control_mode == VA_RC_CBR /*|| rate_control_mode ==
> VA_RC_VBR*/) {
> + if (rate_control_mode == VA_RC_CBR || rate_control_mode ==
> VA_RC_VBR) {
> gen8_mfc_stop(ctx, encode_state, encoder_context,
> ¤t_frame_bits_size);
> sts = intel_mfc_brc_postpack(encode_state, encoder_context,
> current_frame_bits_size);
> if (sts == BRC_NO_HRD_VIOLATION) {
> diff --git a/src/i965_drv_video.c b/src/i965_drv_video.c
> index 76cb915..cc37190 100644
> --- a/src/i965_drv_video.c
> +++ b/src/i965_drv_video.c
> @@ -936,7 +936,10 @@ i965_GetConfigAttributes(VADriverContextP ctx,
> profile != VAProfileMPEG2Simple)
> attrib_list[i].value |= VA_RC_CBR;
>
> - if (profile == VAProfileVP9Profile0)
> + if (profile == VAProfileVP9Profile0 ||
> + profile == VAProfileH264ConstrainedBaseline ||
> + profile == VAProfileH264Main ||
> + profile == VAProfileH264High)
> attrib_list[i].value |= VA_RC_VBR;
>
> break;
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