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[v2,0/2] add MBR type rate control for encoder

Message ID 20240130112400.2636143-1-quic_sachinku@quicinc.com
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Series add MBR type rate control for encoder | expand

Message

Sachin Kumar Garg Jan. 30, 2024, 11:23 a.m. UTC 
This series adds the support for MBR rate control type in the
venus driver.
This rate control type will limit the frame level maximum bitrate as
per the target bitrate.
It will improve the video quality of low motion video at ultra low
bit-rates.

Sachin Kumar Garg (2):
  media: v4l2-ctrls: add encoder maximum bitrate control
  media: venus: add new rate control type MBR for encoder

 Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst | 2 ++
 drivers/media/platform/qcom/venus/hfi_cmds.c              | 7 +++++++
 drivers/media/platform/qcom/venus/hfi_helper.h            | 1 +
 drivers/media/platform/qcom/venus/venc.c                  | 2 ++
 drivers/media/platform/qcom/venus/venc_ctrls.c            | 5 +++--
 drivers/media/v4l2-core/v4l2-ctrls-defs.c                 | 1 +
 include/uapi/linux/v4l2-controls.h                        | 1 +
 7 files changed, 17 insertions(+), 2 deletions(-)

Comments

Nicolas Dufresne Feb. 9, 2024, 3:10 p.m. UTC | #1 
Hi Scahin,

Le mardi 30 janvier 2024 à 16:53 +0530, Sachin Kumar Garg a écrit :
> Introduce V4L2_MPEG_VIDEO_BITRATE_MODE_MBR rate control to
> limit the frame level maximum bit rate.
> Encoder will choose appropriate quantization parameter and
> do the smart bit allocation to set the frame maximum bitrate
> level as per the Bitrate value configured.
> 
> Signed-off-by: Sachin Kumar Garg <quic_sachinku@quicinc.com>
> ---
>  Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst | 2 ++
>  drivers/media/v4l2-core/v4l2-ctrls-defs.c                 | 1 +
>  include/uapi/linux/v4l2-controls.h                        | 1 +
>  3 files changed, 4 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> index 2a165ae063fb..05ef4a70e3f5 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -576,6 +576,8 @@ enum v4l2_mpeg_video_bitrate_mode -
>        - Constant bitrate
>      * - ``V4L2_MPEG_VIDEO_BITRATE_MODE_CQ``
>        - Constant quality
> +    * - ``V4L2_MPEG_VIDEO_BITRATE_MODE_MBR``
> +      - Maximum bitrate

I'm afraid for this one your documentation is too short. I believe your commit
message helps, but this is not what our uAPI users will read.

My understanding is that this feature is a form of constant quality (smart bit
allocation) but with a maximum rate guaranty. Using a specific mode (rather then
a constraint on top of a constant quality mode) is a Qualcomm specific design. I
think presets are generally easier to use, so I kind of like it. What is missing
(arguably all these modes documentation are also missing it) is the rate
observation window. Would be nice to check if there is a way to specify that (or
even configure it, if so add a cross reference).

So I'd like to see some proper documentation for this one, remember that V4L2
documentation is also a specification and will serve to ensure drivers conforms
to the preset expectations.

regards,
Nicolas

>  
>  
>  
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> index 8696eb1cdd61..e0597b61ffb9 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> @@ -154,6 +154,7 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
>  		"Variable Bitrate",
>  		"Constant Bitrate",
>  		"Constant Quality",
> +		"Maximum Bitrate",
>  		NULL
>  	};
>  	static const char * const mpeg_stream_type[] = {
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> index 99c3f5e99da7..7c74d6c417d1 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -393,6 +393,7 @@ enum v4l2_mpeg_video_bitrate_mode {
>  	V4L2_MPEG_VIDEO_BITRATE_MODE_VBR = 0,
>  	V4L2_MPEG_VIDEO_BITRATE_MODE_CBR = 1,
>  	V4L2_MPEG_VIDEO_BITRATE_MODE_CQ  = 2,
> +	V4L2_MPEG_VIDEO_BITRATE_MODE_MBR = 3,
>  };
>  #define V4L2_CID_MPEG_VIDEO_BITRATE		(V4L2_CID_CODEC_BASE+207)
>  #define V4L2_CID_MPEG_VIDEO_BITRATE_PEAK	(V4L2_CID_CODEC_BASE+208)