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Date: Thu, 04 Feb 2021 10:21:04 +0530
From: dikshita@...eaurora.org
To: Hans Verkuil <hverkuil-cisco@...all.nl>
Cc: linux-media@...r.kernel.org, stanimir.varbanov@...aro.org,
linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
vgarodia@...eaurora.org
Subject: Re: [PATCH v6 1/2] media: v4l2-ctrl: add controls for long term
reference.
On 2021-02-01 16:40, Hans Verkuil wrote:
> On 25/01/2021 06:51, Dikshita Agarwal wrote:
>> Long Term Reference (LTR) frames are the frames that are encoded
>> sometime in the past and stored in the DPB buffer list to be used
>> as reference to encode future frames.
>> This change adds controls to enable this feature.
>>
>> Signed-off-by: Dikshita Agarwal <dikshita@...eaurora.org>
>> ---
>> .../userspace-api/media/v4l/ext-ctrls-codec.rst | 18
>> ++++++++++++++++++
>> drivers/media/v4l2-core/v4l2-ctrls.c | 14
>> ++++++++++++++
>> include/uapi/linux/v4l2-controls.h | 3 +++
>> 3 files changed, 35 insertions(+)
>>
>> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> index 400774c..a37d460 100644
>> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> @@ -3637,3 +3637,21 @@ enum v4l2_mpeg_video_hevc_size_of_length_field
>> -
>> - Selecting this value specifies that HEVC slices are expected
>> to be prefixed by Annex B start codes. According to
>> :ref:`hevc`
>> valid start codes can be 3-bytes 0x000001 or 4-bytes
>> 0x00000001.
>> +
>> +``V4L2_CID_MPEG_VIDEO_LTR_COUNT (integer)``
>> + Specifies the number of Long Term Reference (LTR) frames
>> encoder needs
>
> frames encoder -> frames the encoder
>
>> + to generate or keep. This is applicable to the H264 and HEVC
>> encoders.
>
> Isn't this really the maximum number of LTR frames? I.e., the actual
> number
> of LTR frames is something that is determined by userspace, right?
>
> And you say 'generate or keep': but the encoder doesn't generate LTR
> frames,
> they are marked as such by userspace. So this text would be just: "to
> keep".
>
> Or am I wrong?
>
> Regards,
>
> Hans
>
Hi Hans,
I Will update this as:
Specifies the maximum number of Long Term Reference (LTR) frames at any
given time
that the encoder can keep.
Thanks,
Dikshita
>> +
>> +``V4L2_CID_MPEG_VIDEO_FRAME_LTR_INDEX (integer)``
>> + The current frame is marked as a Long Term Reference (LTR)
>> frame
>> + and given this LTR index which ranges from 0 to LTR_COUNT-1.
>> + This is applicable to the H264 and HEVC encoders and can be
>> applied using
>> + Request API.
>> + Source Rec. ITU-T H.264 (06/2019); Table 7.9
>> +
>> +``V4L2_CID_MPEG_VIDEO_USE_LTR_FRAMES (bitmask)``
>> + Specifies the Long Term Reference (LTR) frame(s) to be used
>> for
>> + encoding the current frame.
>> + This provides a bitmask which consists of bits [0,
>> LTR_COUNT-1].
>> + This is applicable to the H264 and HEVC encoders and can be
>> applied using
>> + Request API.
>> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c
>> b/drivers/media/v4l2-core/v4l2-ctrls.c
>> index 16ab54f..84c1eb8 100644
>> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
>> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
>> @@ -950,6 +950,9 @@ const char *v4l2_ctrl_get_name(u32 id)
>> case V4L2_CID_MPEG_VIDEO_MV_V_SEARCH_RANGE: return "Vertical MV
>> Search Range";
>> case V4L2_CID_MPEG_VIDEO_REPEAT_SEQ_HEADER: return "Repeat Sequence
>> Header";
>> case V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME: return "Force Key Frame";
>> + case V4L2_CID_MPEG_VIDEO_LTR_COUNT: return "LTR Count";
>> + case V4L2_CID_MPEG_VIDEO_FRAME_LTR_INDEX: return "Frame LTR Index";
>> + case V4L2_CID_MPEG_VIDEO_USE_LTR_FRAMES: return "Use LTR Frames";
>> case V4L2_CID_MPEG_VIDEO_MPEG2_SLICE_PARAMS: return "MPEG-2 Slice
>> Parameters";
>> case V4L2_CID_MPEG_VIDEO_MPEG2_QUANTIZATION: return "MPEG-2
>> Quantization Matrices";
>> case V4L2_CID_FWHT_I_FRAME_QP: return "FWHT I-Frame QP Value";
>> @@ -1277,6 +1280,17 @@ void v4l2_ctrl_fill(u32 id, const char **name,
>> enum v4l2_ctrl_type *type,
>> case V4L2_CID_MPEG_VIDEO_MV_V_SEARCH_RANGE:
>> *type = V4L2_CTRL_TYPE_INTEGER;
>> break;
>> + case V4L2_CID_MPEG_VIDEO_LTR_COUNT:
>> + *type = V4L2_CTRL_TYPE_INTEGER;
>> + break;
>> + case V4L2_CID_MPEG_VIDEO_FRAME_LTR_INDEX:
>> + *type = V4L2_CTRL_TYPE_INTEGER;
>> + *flags |= V4L2_CTRL_FLAG_EXECUTE_ON_WRITE;
>> + break;
>> + case V4L2_CID_MPEG_VIDEO_USE_LTR_FRAMES:
>> + *type = V4L2_CTRL_TYPE_BITMASK;
>> + *flags |= V4L2_CTRL_FLAG_EXECUTE_ON_WRITE;
>> + break;
>> case V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME:
>> case V4L2_CID_PAN_RESET:
>> case V4L2_CID_TILT_RESET:
>> diff --git a/include/uapi/linux/v4l2-controls.h
>> b/include/uapi/linux/v4l2-controls.h
>> index af8dda2..c0bb87b 100644
>> --- a/include/uapi/linux/v4l2-controls.h
>> +++ b/include/uapi/linux/v4l2-controls.h
>> @@ -422,6 +422,9 @@ enum v4l2_mpeg_video_multi_slice_mode {
>> #define
>> V4L2_CID_MPEG_VIDEO_MV_H_SEARCH_RANGE (V4L2_CID_CODEC_BASE+227)
>> #define
>> V4L2_CID_MPEG_VIDEO_MV_V_SEARCH_RANGE (V4L2_CID_CODEC_BASE+228)
>> #define
>> V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME (V4L2_CID_CODEC_BASE+229)
>> +#define V4L2_CID_MPEG_VIDEO_LTR_COUNT (V4L2_CID_CODEC_BASE+230)
>> +#define
>> V4L2_CID_MPEG_VIDEO_FRAME_LTR_INDEX (V4L2_CID_CODEC_BASE+231)
>> +#define V4L2_CID_MPEG_VIDEO_USE_LTR_FRAMES (V4L2_CID_CODEC_BASE+232)
>>
>> /* CIDs for the MPEG-2 Part 2 (H.262) codec */
>> #define V4L2_CID_MPEG_VIDEO_MPEG2_LEVEL (V4L2_CID_CODEC_BASE+270)
>>
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