[FFmpeg-devel] [PATCH 1/3] lavc/mjpegdec: add function ff_mjpeg_decode_header

[Michael Niedermayer]

On Thu, Jun 27, 2019 at 08:59:12PM +0800, Zhong Li wrote:
> It will be reused in the following mjpeg_parser patch
> 
> Signed-off-by: Zhong Li <zhong.li at intel.com>
> ---
> Mark Thompson: This seems suspicious - MJPEG is generally 4:2:2 (e.g. UVC requires it), so I would expect a 4:2:2 format to be the default here?  (Or maybe a longer list - VAAPI certainly supports 4:2:2, 4:2:0 and 4:4:4 on the same hardware.)
> Zhong: libmfx can support jpeg baseline profile with more output formats, but current ffmpeg-qsv decoder/vpp can't. Will extend supported format list as separated patch.
> 
>  libavcodec/mjpegdec.c | 37 ++++++++++++++++++++++++++++---------
>  libavcodec/mjpegdec.h |  4 ++++
>  2 files changed, 32 insertions(+), 9 deletions(-)
> 
> diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
> index a65bc8d..5da66bb 100644
> --- a/libavcodec/mjpegdec.c
> +++ b/libavcodec/mjpegdec.c
> @@ -157,6 +157,8 @@ av_cold int ff_mjpeg_decode_init(AVCodecContext *avctx)
>      s->start_code    = -1;
>      s->first_picture = 1;
>      s->got_picture   = 0;
> +    s->reinit_idct   = 0;
> +    s->size_change   = 0;
>      s->org_height    = avctx->coded_height;
>      avctx->chroma_sample_location = AVCHROMA_LOC_CENTER;
>      avctx->colorspace = AVCOL_SPC_BT470BG;
> @@ -302,9 +304,9 @@ int ff_mjpeg_decode_dht(MJpegDecodeContext *s)
>      return 0;
>  }
>  
> -int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
> +int ff_mjpeg_decode_header(MJpegDecodeContext *s)
>  {
> -    int len, nb_components, i, width, height, bits, ret, size_change;
> +    int len, nb_components, i, width, height, bits, ret;
>      unsigned pix_fmt_id;
>      int h_count[MAX_COMPONENTS] = { 0 };
>      int v_count[MAX_COMPONENTS] = { 0 };
> @@ -324,7 +326,7 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
>      if (s->avctx->bits_per_raw_sample != bits) {
>          av_log(s->avctx, s->avctx->bits_per_raw_sample > 0 ? AV_LOG_INFO : AV_LOG_DEBUG, "Changing bps from %d to %d\n", s->avctx->bits_per_raw_sample, bits);
>          s->avctx->bits_per_raw_sample = bits;
> -        init_idct(s->avctx);
> +        s->reinit_idct = 1;
>      }

I think the avctx->bits_per_raw_sample value should stay in sync with
the initialized idct

This patch would allow the bits_per_raw_sample to change and then
a subsequent error to skip init_idct()
maybe this is ok as it would be probably called later in a subsequent
frame but i think its better if they stay closer together or there
is nothing between them that can cause ine to exeucute without the other

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

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