[PATCH v5 03/11] media: uapi: h264: Add the concept of decoding mode

Ezequiel Garcia
2019-08-12T19:35:58Z

From: Boris Brezillon <boris.brezillon@collabora.com>

Some stateless decoders don't support per-slice decoding granularity
(or at least not in a way that would make them efficient or easy to use).

Expose a menu to control the supported decoding modes. Drivers are
allowed to support only one decoding but they can support both too.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
---
Changes in v5:
* Improve specification as suggested by Hans.
Changes in v4:
* Typos/rewording fixes
Changes in v3:
* s/per-{slice,frame} decoding/{slice,frame}-based decoding/
* Add Paul's R-b
Changes in v2:
* Allow decoding multiple slices in per-slice decoding mode
* Minor doc improvement/fixes
---
.../media/uapi/v4l/ext-ctrls-codec.rst | 47 ++++++++++++++++++-
.../media/uapi/v4l/pixfmt-compressed.rst | 3 +-
drivers/media/v4l2-core/v4l2-ctrls.c | 9 ++++
include/media/h264-ctrls.h | 11 +++++
4 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/Documentation/media/uapi/v4l/ext-ctrls-codec.rst b/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
index c5f39dd50043..568390273fde 100644
--- a/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
+++ b/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
@@ -1747,6 +1747,11 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
* - __u32
- ``size``
-
+ * - __u32
+ - ``start_byte_offset``
+ - Where the slice payload starts in the output buffer. Useful when the
+ OUTPUT buffer contains more than one slice (some codecs need to know
+ where each slice starts in this buffer).
* - __u32
- ``header_bit_size``
-
@@ -1930,7 +1935,10 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
-
* - __u16
- ``num_slices``
- - Number of slices needed to decode the current frame
+ - Number of slices needed to decode the current frame/field. When
+ operating in slice-based decoding mode (see
+ :c:type:`v4l2_mpeg_video_h264_decoding_mode`), this field
+ should always be set to one.
* - __u16
- ``nal_ref_idc``
- NAL reference ID value coming from the NAL Unit header
@@ -2021,6 +2029,43 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
- 0x00000004
- The DPB entry is a long term reference frame

+``V4L2_CID_MPEG_VIDEO_H264_DECODING_MODE (enum)``
+ Specifies the decoding mode to use. Currently exposes slice-based and
+ frame-based decoding but new modes might be added later on.
+ This control is used to complement V4L2_PIX_FMT_H264_SLICE
+ pixel format. Applications that support V4L2_PIX_FMT_H264_SLICE
+ are required to set this control in order to specify the decoding mode
+ that is expected for the buffer.
+ Drivers may expose a single or multiple decoding modes, depending
+ on what they can support.
+
+ .. note::
+
+ This menu control is not yet part of the public kernel API and
+ it is expected to change.
+
+.. c:type:: v4l2_mpeg_video_h264_decoding_mode
+
+.. cssclass:: longtable
+
+.. flat-table::
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 1 2
+
+ * - ``V4L2_MPEG_VIDEO_H264_SLICE_BASED_DECODING``
+ - 0
+ - The decoding is done at the slice granularity.
+ v4l2_ctrl_h264_decode_params->num_slices should be set to 1.
+ The OUTPUT buffer must contain a single slice.
+ * - ``V4L2_MPEG_VIDEO_H264_FRAME_BASED_DECODING``
+ - 1
+ - The decoding is done at the frame granularity.
+ v4l2_ctrl_h264_decode_params->num_slices should be set to the number of
+ slices forming a frame.
+ The OUTPUT buffer must contain all slices needed to decode the
+ frame. The OUTPUT buffer must also contain both fields.
+
.. _v4l2-mpeg-mpeg2:

``V4L2_CID_MPEG_VIDEO_MPEG2_SLICE_PARAMS (struct)``
diff --git a/Documentation/media/uapi/v4l/pixfmt-compressed.rst b/Documentation/media/uapi/v4l/pixfmt-compressed.rst
index 9b65473a2288..50557c85d99d 100644
--- a/Documentation/media/uapi/v4l/pixfmt-compressed.rst
+++ b/Documentation/media/uapi/v4l/pixfmt-compressed.rst
@@ -61,7 +61,8 @@ Compressed Formats
stateless video decoders that implement an H264 pipeline
(using the :ref:`mem2mem` and :ref:`media-request-api`).
Metadata associated with the frame to decode are required to
- be passed through the ``V4L2_CID_MPEG_VIDEO_H264_SPS``,
+ be passed through the ``V4L2_CID_MPEG_VIDEO_H264_DECODING_MODE``,
+ ``V4L2_CID_MPEG_VIDEO_H264_SPS``,
``V4L2_CID_MPEG_VIDEO_H264_PPS``,
``V4L2_CID_MPEG_VIDEO_H264_SCALING_MATRIX``,
``V4L2_CID_MPEG_VIDEO_H264_SLICE_PARAMS`` and
diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index cd1ae016706f..c3194299bfac 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -402,6 +402,11 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
"Explicit",
NULL,
};
+ static const char * const h264_decoding_mode[] = {
+ "Slice-Based",
+ "Frame-Based",
+ NULL,
+ };
static const char * const mpeg_mpeg2_level[] = {
"Low",
"Main",
@@ -633,6 +638,8 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
return h264_fp_arrangement_type;
case V4L2_CID_MPEG_VIDEO_H264_FMO_MAP_TYPE:
return h264_fmo_map_type;
+ case V4L2_CID_MPEG_VIDEO_H264_DECODING_MODE:
+ return h264_decoding_mode;
case V4L2_CID_MPEG_VIDEO_MPEG2_LEVEL:
return mpeg_mpeg2_level;
case V4L2_CID_MPEG_VIDEO_MPEG2_PROFILE:
@@ -852,6 +859,7 @@ const char *v4l2_ctrl_get_name(u32 id)
case V4L2_CID_MPEG_VIDEO_H264_SCALING_MATRIX: return "H264 Scaling Matrix";
case V4L2_CID_MPEG_VIDEO_H264_SLICE_PARAMS: return "H264 Slice Parameters";
case V4L2_CID_MPEG_VIDEO_H264_DECODE_PARAMS: return "H264 Decode Parameters";
+ case V4L2_CID_MPEG_VIDEO_H264_DECODING_MODE: return "H264 Decoding Mode";
case V4L2_CID_MPEG_VIDEO_MPEG2_LEVEL: return "MPEG2 Level";
case V4L2_CID_MPEG_VIDEO_MPEG2_PROFILE: return "MPEG2 Profile";
case V4L2_CID_MPEG_VIDEO_MPEG4_I_FRAME_QP: return "MPEG4 I-Frame QP Value";
@@ -1220,6 +1228,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
case V4L2_CID_MPEG_VIDEO_H264_VUI_SAR_IDC:
case V4L2_CID_MPEG_VIDEO_H264_SEI_FP_ARRANGEMENT_TYPE:
case V4L2_CID_MPEG_VIDEO_H264_FMO_MAP_TYPE:
+ case V4L2_CID_MPEG_VIDEO_H264_DECODING_MODE:
case V4L2_CID_MPEG_VIDEO_MPEG2_LEVEL:
case V4L2_CID_MPEG_VIDEO_MPEG2_PROFILE:
case V4L2_CID_MPEG_VIDEO_MPEG4_LEVEL:
diff --git a/include/media/h264-ctrls.h b/include/media/h264-ctrls.h
index 6160a69c0143..e6c510877f67 100644
--- a/include/media/h264-ctrls.h
+++ b/include/media/h264-ctrls.h
@@ -26,6 +26,7 @@
#define V4L2_CID_MPEG_VIDEO_H264_SCALING_MATRIX (V4L2_CID_MPEG_BASE+1002)
#define V4L2_CID_MPEG_VIDEO_H264_SLICE_PARAMS (V4L2_CID_MPEG_BASE+1003)
#define V4L2_CID_MPEG_VIDEO_H264_DECODE_PARAMS (V4L2_CID_MPEG_BASE+1004)
+#define V4L2_CID_MPEG_VIDEO_H264_DECODING_MODE (V4L2_CID_MPEG_BASE+1005)

/* enum v4l2_ctrl_type type values */
#define V4L2_CTRL_TYPE_H264_SPS 0x0110
@@ -33,6 +34,12 @@
#define V4L2_CTRL_TYPE_H264_SCALING_MATRIX 0x0112
#define V4L2_CTRL_TYPE_H264_SLICE_PARAMS 0x0113
#define V4L2_CTRL_TYPE_H264_DECODE_PARAMS 0x0114
+#define V4L2_CTRL_TYPE_H264_DECODING_MODE 0x0115
+
+enum v4l2_mpeg_video_h264_decoding_mode {
+ V4L2_MPEG_VIDEO_H264_SLICE_BASED_DECODING,
+ V4L2_MPEG_VIDEO_H264_FRAME_BASED_DECODING,
+};

#define V4L2_H264_SPS_CONSTRAINT_SET0_FLAG 0x01
#define V4L2_H264_SPS_CONSTRAINT_SET1_FLAG 0x02
@@ -125,6 +132,10 @@ struct v4l2_h264_pred_weight_table {
struct v4l2_ctrl_h264_slice_params {
/* Size in bytes, including header */
__u32 size;
+
+ /* Offset in bytes to the start of slice in the OUTPUT buffer. */
+ __u32 start_byte_offset;
+
/* Offset in bits to slice_data() from the beginning of this slice. */
__u32 header_bit_size;

--
2.22.0