Re: Re: [PATCH v6 11/17] media: uapi: Add... | linux-arm-kernel

quoted

Dne torek, 31. maj 2022 ob 08:58:46 CEST je Benjamin Gaignard napisal(a):
Le 30/05/2022 à 23:24, Jernej Škrabec a écrit :
Dne ponedeljek, 30. maj 2022 ob 15:49:57 CEST je Hans Verkuil napisal(a):
On 30/05/2022 11:18, Hans Verkuil wrote:
On 29/05/2022 08:40, Jernej Škrabec wrote:
Hi!

This series looks very good and I plan to test it shortly on Cedrus, 
but
I
have one major concern below.

Dne petek, 27. maj 2022 ob 16:31:28 CEST je Benjamin Gaignard 
napisal(a):
The number of 'entry point offset' can be very variable.
Instead of using a large static array define a v4l2 dynamic array
of U32 (V4L2_CTRL_TYPE_U32).
The number of entry point offsets is reported by the elems field
and in struct v4l2_ctrl_hevc_slice_params.num_entry_point_offsets
field.
Slice control by itself is variable length array, so you would actually
need
2D variable array for entry points which is not supported. However, 
easy
workaround for that is to flatten 2D array to 1D and either have another
slice
control field which would tell first entry point index for convenience or
let
driver calculate it by adding up all num_entry_point_offsets of previous
slices.

Hans, what do you think?
If I would support 2D variable array sizes, wouldn't that be more 
elegant?
The current implementation doesn't support that, but as the commit log 
for
patch 1/17 says:

"Currently dynamically sized arrays are limited to one dimensional 
arrays,
but that might change in the future if there is a need for it."

Let me know if you agree, and I'll try to implement this. It's been a
while
since I last looked at this, so I'm not sure how much work it is, but it
is
probably worth a shot.
Digging more into this made me realize that this doesn't actually help 
for
this
particular case.

I would lean towards your second suggestion of adding up all
num_entry_point_offsets
of previous slices.
Just one question/clarification about dynamic arrays - does driver need to
reserve maximum amount of memory for dynamic array control at 
initialization
time? If so, this would still be problematic, since there cound be a huge
amount of entry points in theory.
When adding the control the driver could set .dims field to specify
the max number of accepted slices.
I have added '#define V4L2_HEVC_SLICE_MAX_COUNT 600' that you could use
for this field. It is the value we have found when using slices with RKVDEC
driver.
Is this maximum value applicable only to RKVDEC or is universal? Anyway, this 
means maximum offset points control for Cedrus would be 600 * 1024 (max. offset 
points supported per slice) * 4 ~= 2.4 MB, which is a lot for one control, but 
I can live with that...

Best regards,
Jernej

Regards,
Benjamin

Best regards,
Jernej

Regards,

	Hans

Regards,

	Hans

Note, it seems that H265 decoding on Cedrus still works without entry
points,
so this problem can be solved later. I'm not sure what we lose with 
that
but
it was suggested that this could influence speed or error resilience or
both.
However, I think we're close to solve it, so I'd like to do that now.

Best regards,
Jernej

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
---
  .../userspace-api/media/v4l/ext-ctrls-codec.rst       | 11 +++++++++
++
  drivers/media/v4l2-core/v4l2-ctrls-defs.c             |  5 +++++
  include/media/hevc-ctrls.h                            |  5 ++++-
  3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst 
b/
Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
index 0796b1563daa..05228e280f66 100644
--- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
+++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
@@ -3010,6 +3010,9 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
      * - __u32
        - ``data_bit_offset``
        - Offset (in bits) to the video data in the current slice data.
+    * - __u32
+      - ``num_entry_point_offsets``
+      - Specifies the number of entry point offset syntax elements in 
the
slice header.
      * - __u8
        - ``nal_unit_type``
        - Specifies the coding type of the slice (B, P or I).
@@ -3150,6 +3153,14 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
  
      \normalsize
  
+``V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS (integer)``
+    Specifies entry point offsets in bytes.
+    This control is a dynamically sized array. The number of entry
point
+    offsets is reported by the ``elems`` field.
+    This bitstream parameter is defined according to :ref:`hevc`.
+    They are described in section 7.4.7.1 "General slice segment 
header
+    semantics" of the specification.
+
  ``V4L2_CID_STATELESS_HEVC_SCALING_MATRIX (struct)``
      Specifies the HEVC scaling matrix parameters used for the scaling
process
      for transform coefficients.
diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/
v4l2-
core/v4l2-ctrls-defs.c
index d594efbcbb93..e22921e7ea61 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
@@ -1188,6 +1188,7 @@ const char *v4l2_ctrl_get_name(u32 id)
  	case V4L2_CID_STATELESS_HEVC_DECODE_PARAMS:		return
"HEVC Decode Parameters";
  	case V4L2_CID_STATELESS_HEVC_DECODE_MODE:		return
"HEVC Decode Mode";
  	case V4L2_CID_STATELESS_HEVC_START_CODE:		return
"HEVC Start Code";
+	case V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS:	return
"HEVC Entry Point Offsets";
  
  	/* Colorimetry controls */
  	/* Keep the order of the 'case's the same as in v4l2-controls.h!
*/
@@ -1518,6 +1519,10 @@ void v4l2_ctrl_fill(u32 id, const char **name,
enum
v4l2_ctrl_type *type,
  	case V4L2_CID_STATELESS_HEVC_DECODE_PARAMS:
  		*type = V4L2_CTRL_TYPE_HEVC_DECODE_PARAMS;
  		break;
+	case V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS:
+		*type = V4L2_CTRL_TYPE_U32;
+		*flags |= V4L2_CTRL_FLAG_DYNAMIC_ARRAY;
+		break;
  	case V4L2_CID_STATELESS_VP9_COMPRESSED_HDR:
  		*type = V4L2_CTRL_TYPE_VP9_COMPRESSED_HDR;
  		break;
diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
index a3c829ef531a..1319cb99ae3f 100644
--- a/include/media/hevc-ctrls.h
+++ b/include/media/hevc-ctrls.h
@@ -20,6 +20,7 @@
  #define V4L2_CID_STATELESS_HEVC_DECODE_PARAMS	
(V4L2_CID_CODEC_BASE
+ 1012)
  #define V4L2_CID_STATELESS_HEVC_DECODE_MODE	
(V4L2_CID_CODEC_BASE
+ 1015)
  #define V4L2_CID_STATELESS_HEVC_START_CODE	
(V4L2_CID_CODEC_BASE + 1016)
+#define V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS 
(V4L2_CID_CODEC_BASE
+
1017)
  
  /* enum v4l2_ctrl_type type values */
  #define V4L2_CTRL_TYPE_HEVC_SPS 0x0120
@@ -318,6 +319,8 @@ struct v4l2_hevc_pred_weight_table {
   *
   * @bit_size: size (in bits) of the current slice data
   * @data_bit_offset: offset (in bits) to the video data in the current
slice
data
+ * @num_entry_point_offsets: specifies the number of entry point offset
syntax
+ *			     elements in the slice header.
   * @nal_unit_type: specifies the coding type of the slice (B, P or I)
   * @nuh_temporal_id_plus1: minus 1 specifies a temporal identifier for
the
NAL unit
   * @slice_type: see V4L2_HEVC_SLICE_TYPE_{}
@@ -360,7 +363,7 @@ struct v4l2_hevc_pred_weight_table {
  struct v4l2_ctrl_hevc_slice_params {
  	__u32	bit_size;
  	__u32	data_bit_offset;
-
+	__u32	num_entry_point_offsets;
  	/* ISO/IEC 23008-2, ITU-T Rec. H.265: NAL unit header */
  	__u8	nal_unit_type;
  	__u8	nuh_temporal_id_plus1;
-- 
2.32.0



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