media: uapi: mpeg2: rework quantisation matrices semantics

As stated in the MPEG-2 specification, section 6.3.7 "Quant matrix
extension":

  Each quantisation matrix has a default set of values. When a
  sequence_header_code is decoded all matrices shall be reset to
  their default values. User defined matrices may be downloaded
  and this can occur in a sequence_header() or in a
  quant_matrix_extension().

The load_intra_quantiser_matrix syntax elements are transmitted
in the bitstream headers, signalling that a quantisation matrix
needs to be loaded and used for pictures transmitted afterwards
(until the matrices are reset).

This "load" semantics are implemented in the V4L2 interface
without the need of any "load" flags: passing the control
is effectively a load.

Therefore, rework the V4L2_CID_MPEG_VIDEO_MPEG2_QUANTISATION
semantics to match the MPEG-2 semantics. Quantisation matrices
values are now initialized by the V4L2 control core to their
reset default value, and applications are expected to reset
their values as specified.

The quantisation control is therefore optional, and used to
load bitstream-defined values in the quantisation matrices.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Co-developed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Tested-by: Jernej Skrabec <jernej.skrabec@siol.net>
Reviewed-by: Jernej Skrabec <jernej.skrabec@siol.net>
Tested-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

1 files changed, 26 insertions, 0 deletions

diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index 1ed62f0ed66f..41955ea9230d 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -57,6 +57,18 @@ static bool is_new_manual(const struct v4l2_ctrl *master)
 	return master->is_auto && master->val == master->manual_mode_value;
 }
 
+/* Default intra MPEG-2 quantisation coefficients, from the specification. */
+static const u8 mpeg2_intra_quant_matrix[64] = {
+	8,  16, 16, 19, 16, 19, 22, 22,
+	22, 22, 22, 22, 26, 24, 26, 27,
+	27, 27, 26, 26, 26, 26, 27, 27,
+	27, 29, 29, 29, 34, 34, 34, 29,
+	29, 29, 27, 27, 29, 29, 32, 32,
+	34, 34, 37, 38, 37, 35, 35, 34,
+	35, 38, 38, 40, 40, 40, 48, 48,
+	46, 46, 56, 56, 58, 69, 69, 83
+};
+
 /* Returns NULL or a character pointer array containing the menu for
    the given control ID. The pointer array ends with a NULL pointer.
    An empty string signifies a menu entry that is invalid. This allows
@@ -1692,6 +1704,7 @@ static void std_init_compound(const struct v4l2_ctrl *ctrl, u32 idx,
 			      union v4l2_ctrl_ptr ptr)
 {
 	struct v4l2_ctrl_mpeg2_slice_params *p_mpeg2_slice_params;
+	struct v4l2_ctrl_mpeg2_quantisation *p_mpeg2_quant;
 	struct v4l2_ctrl_vp8_frame *p_vp8_frame;
 	struct v4l2_ctrl_fwht_params *p_fwht_params;
 	void *p = ptr.p + idx * ctrl->elem_size;
@@ -1716,6 +1729,19 @@ static void std_init_compound(const struct v4l2_ctrl *ctrl, u32 idx,
 		p_mpeg2_slice_params->picture.picture_coding_type =
 					V4L2_MPEG2_PICTURE_CODING_TYPE_I;
 		break;
+	case V4L2_CTRL_TYPE_MPEG2_QUANTISATION:
+		p_mpeg2_quant = p;
+
+		memcpy(p_mpeg2_quant->intra_quantiser_matrix,
+		       mpeg2_intra_quant_matrix,
+		       ARRAY_SIZE(mpeg2_intra_quant_matrix));
+		/*
+		 * The default non-intra MPEG-2 quantisation
+		 * coefficients are all 16, as per the specification.
+		 */
+		memset(p_mpeg2_quant->non_intra_quantiser_matrix, 16,
+		       sizeof(p_mpeg2_quant->non_intra_quantiser_matrix));
+		break;
 	case V4L2_CTRL_TYPE_VP8_FRAME:
 		p_vp8_frame = p;
 		p_vp8_frame->num_dct_parts = 1;