Re: [PATCH 03/12] media: hantro: Fix H264 motion vector buffer offset

From: Philipp Zabel
Date: Tue Sep 03 2019 - 06:58:47 EST


Hi Jonas,

On Sun, 2019-09-01 at 12:45 +0000, Jonas Karlman wrote:
> A decoded 8-bit 4:2:0 frame need memory for up to 448 macroblocks
> and is laid out in memory as follow:

Do you mean "A decoded 8-bit 4:2:0 frame needs up to 448 bytes per
macroblock"?

A 1280x720 frame already consists of 3600 macroblocks (each 16x16 Y +
2x8x8 Cb,Cr).

> +-------------------+
> > Y-plane 256 MBs |

So that looks like it should be 256 bytes * number of macroblocks
instead, same for the following two.

> +-------------------+
> > UV-plane 128 MBs |
> +-------------------+
> > MV buffer 64 MBs |
>
> +-------------------+
>
> The motion vector buffer offset is currently correct for 4:2:0 because
> the extra space for motion vectors is overallocated with an extra 64 MBs.
>
> Wrong offset for both destination and motion vector buffer are used
> for the bottom field of field encoded content, wrong offset is
> also used for 4:0:0 (monochrome) content.
>
> Fix this by always setting the motion vector address to the expected
> 384 MBs offset for 4:2:0 and 256 MBs offset for 4:0:0 content.

Expected by whom? For example, could these be placed in separate buffers
instead of appended to the VB2 allocated buffers?

> Also use correct destination and motion vector buffer offset
> for the bottom field of field encoded content.
>
> While at it also extend the check for 4:0:0 (monochrome) to include an
> additional check for High Profile (100).
>
> Fixes: dea0a82f3d22 ("media: hantro: Add support for H264 decoding on G1")
> Signed-off-by: Jonas Karlman <jonas@xxxxxxxxx>
> ---
> .../staging/media/hantro/hantro_g1_h264_dec.c | 33 +++++++++++--------
> 1 file changed, 19 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/staging/media/hantro/hantro_g1_h264_dec.c b/drivers/staging/media/hantro/hantro_g1_h264_dec.c
> index 7ab534936843..159bd67e0a36 100644
> --- a/drivers/staging/media/hantro/hantro_g1_h264_dec.c
> +++ b/drivers/staging/media/hantro/hantro_g1_h264_dec.c
> @@ -19,6 +19,9 @@
> #include "hantro_hw.h"
> #include "hantro_v4l2.h"
>
> +#define MV_OFFSET_420 384
> +#define MV_OFFSET_400 256
> +
> static void set_params(struct hantro_ctx *ctx)
> {
> const struct hantro_h264_dec_ctrls *ctrls = &ctx->h264_dec.ctrls;
> @@ -49,8 +52,8 @@ static void set_params(struct hantro_ctx *ctx)
> vdpu_write_relaxed(vpu, reg, G1_REG_DEC_CTRL0);
>
> /* Decoder control register 1. */
> - reg = G1_REG_DEC_CTRL1_PIC_MB_WIDTH(sps->pic_width_in_mbs_minus1 + 1) |
> - G1_REG_DEC_CTRL1_PIC_MB_HEIGHT_P(sps->pic_height_in_map_units_minus1 + 1) |
> + reg = G1_REG_DEC_CTRL1_PIC_MB_WIDTH(H264_MB_WIDTH(ctx->dst_fmt.width)) |
> + G1_REG_DEC_CTRL1_PIC_MB_HEIGHT_P(H264_MB_HEIGHT(ctx->dst_fmt.height)) |
> G1_REG_DEC_CTRL1_REF_FRAMES(sps->max_num_ref_frames);
> vdpu_write_relaxed(vpu, reg, G1_REG_DEC_CTRL1);
>
> @@ -79,7 +82,7 @@ static void set_params(struct hantro_ctx *ctx)
> reg |= G1_REG_DEC_CTRL4_CABAC_E;
> if (sps->flags & V4L2_H264_SPS_FLAG_DIRECT_8X8_INFERENCE)
> reg |= G1_REG_DEC_CTRL4_DIR_8X8_INFER_E;
> - if (sps->chroma_format_idc == 0)
> + if (sps->profile_idc >= 100 && sps->chroma_format_idc == 0)
> reg |= G1_REG_DEC_CTRL4_BLACKWHITE_E;
> if (pps->flags & V4L2_H264_PPS_FLAG_WEIGHTED_PRED)
> reg |= G1_REG_DEC_CTRL4_WEIGHT_PRED_E;
> @@ -233,6 +236,7 @@ static void set_buffers(struct hantro_ctx *ctx)
> struct vb2_v4l2_buffer *src_buf, *dst_buf;
> struct hantro_dev *vpu = ctx->dev;
> dma_addr_t src_dma, dst_dma;
> + unsigned int offset = MV_OFFSET_420;
>
> src_buf = hantro_get_src_buf(ctx);
> dst_buf = hantro_get_dst_buf(ctx);
> @@ -243,19 +247,20 @@ static void set_buffers(struct hantro_ctx *ctx)
>
> /* Destination (decoded frame) buffer. */
> dst_dma = vb2_dma_contig_plane_dma_addr(&dst_buf->vb2_buf, 0);
> + if (ctrls->slices[0].flags & V4L2_H264_SLICE_FLAG_BOTTOM_FIELD)
> + dst_dma += ALIGN(ctx->dst_fmt.width, H264_MB_DIM);

How does this work? Does userspace decode two fields into the same
capture buffer and the hardware writes each field with a stride of 2
lines? I suppose this corresponds to V4L2_FIELD_INTERLACED. Could this
also be made to support V4L2_FIELD_SEQ_TB output?

regards
Philipp