[FFmpeg-devel] [PATCH] H.264: Record slice_qs_delta syntax element

[Michael Niedermayer]

On Sun, Dec 20, 2009 at 04:30:55PM +0100, Gwenole Beauchesne wrote:
> Hi,
>
> On Sat, 12 Dec 2009, Michael Niedermayer wrote:
>
>> On Fri, Dec 11, 2009 at 03:25:34PM +0100, Gwenole Beauchesne wrote:
>>> Hi,
>>>
>>> slice_qp_delta and slice_qs_delta values from the bitstream are
>>> respectively needed for VAAPI,DXVA and DXVA.
>>
>>> The former could be
>>> reconstructed with a single subtraction though.
>>
>> then i would suggest to do it with a subtraction
>
> This is what we currently do but I felt having both recorded was better for 
> consistency. qscale doesn't seem to be altered elsewhere for h264, so 
> keeping the subtraction is ok for slice_qp_delta.
>
> Anyway, here is a new patch with only slice_qs_delta.
>
> Thanks,
> Gwenole.

>  h264.c |    2 +-
>  h264.h |    2 ++
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 967b28be582c7ea93b8d2dff7953c90a58c8e63e  ffmpeg.h264.record.slice_qs_delta.patch
> commit 30cb151105ea749f3851308698ec501012bdf3e2
> Author: Gwenole Beauchesne <gbeauchesne at splitted-desktop.com>
> Date:   Fri Dec 11 13:51:15 2009 +0000
> 
>     Record slice_qs_delta syntax element.
> 
> diff --git a/libavcodec/h264.c b/libavcodec/h264.c
> index 1bfb1e2..e98ff0a 100644
> --- a/libavcodec/h264.c
> +++ b/libavcodec/h264.c
> @@ -4061,7 +4062,7 @@ static int decode_slice_header(H264Context *h, H264Context *h0){
>          get_bits1(&s->gb); /* sp_for_switch_flag */
>      }
>      if(h->slice_type==FF_SP_TYPE || h->slice_type == FF_SI_TYPE){
> -        get_se_golomb(&s->gb); /* slice_qs_delta */
> +        h->slice_qs_delta = get_se_golomb(&s->gb); /* slice_qs_delta */
>      }
>  
>      h->deblocking_filter = 1;
> diff --git a/libavcodec/h264.h b/libavcodec/h264.h
> index fa348a2..f624bc3 100644
> --- a/libavcodec/h264.h
> +++ b/libavcodec/h264.h
> @@ -545,6 +545,8 @@ typedef struct H264Context{
>      // Timestamp stuff
>      int sei_buffering_period_present;  ///< Buffering period SEI flag
>      int initial_cpb_removal_delay[32]; ///< Initial timestamps for CPBs
> +
> +    int slice_qs_delta; ///< Initial value of QSy

slice_qs_delta is not the initial value of QSy

did you test this code?

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Asymptotically faster algorithms should always be preferred if you have
asymptotical amounts of data
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