[FFmpeg-devel] [PATCH 1/3] lavc/pngdec: honor skip_frame option

[Michael Niedermayer]

On Mon, Oct 19, 2015 at 10:28:18AM +0200, Matthieu Bouron wrote:
> On Sat, Oct 17, 2015 at 10:34:22PM +0200, Matthieu Bouron wrote:
> > From: Matthieu Bouron <matthieu.bouron at stupeflix.com>
> > 
> > ---
> >  libavcodec/pngdec.c | 34 ++++++++++++++++++++++++++++++++++
> >  1 file changed, 34 insertions(+)
> > 
> > diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
> > index 4cfdc58..5b2befe 100644
> > --- a/libavcodec/pngdec.c
> > +++ b/libavcodec/pngdec.c
> > @@ -1087,6 +1087,13 @@ static int decode_frame_common(AVCodecContext *avctx, PNGDecContext *s,
> >      for (;;) {
> >          length = bytestream2_get_bytes_left(&s->gb);
> >          if (length <= 0) {
> > +
> > +            if (avctx->codec_id == AV_CODEC_ID_PNG &&
> > +                avctx->skip_frame == AVDISCARD_ALL) {
> > +                av_frame_set_metadata(p, metadata);
> > +                return 0;
> > +            }
> > +
> >              if (CONFIG_APNG_DECODER && avctx->codec_id == AV_CODEC_ID_APNG && length == 0) {
> >                  if (!(s->state & PNG_IDAT))
> >                      return 0;
> > @@ -1114,6 +1121,22 @@ static int decode_frame_common(AVCodecContext *avctx, PNGDecContext *s,
> >                  ((tag >> 8) & 0xff),
> >                  ((tag >> 16) & 0xff),
> >                  ((tag >> 24) & 0xff), length);
> > +
> > +        if (avctx->codec_id == AV_CODEC_ID_PNG &&
> > +            avctx->skip_frame == AVDISCARD_ALL) {
> > +            int i, found = 0;
> > +            static const int tags[] = { MKTAG('I', 'H', 'D', 'R'), MKTAG('t', 'E', 'X', 't'), MKTAG('I', 'D', 'A', 'T') };
> > +            for (i = 0; i < FF_ARRAY_ELEMS(tags); i++) {
> > +                if (tag == tags[i]) {
> > +                    found = 1;
> > +                    break;
> > +                }
> > +            }
> > +            if (!found) {
> > +                goto skip_tag;
> > +            }
> > +        }
> > +
> >          switch (tag) {
> >          case MKTAG('I', 'H', 'D', 'R'):
> >              if ((ret = decode_ihdr_chunk(avctx, s, length)) < 0)
> > @@ -1181,6 +1204,11 @@ skip_tag:
> >          }
> >      }
> >  exit_loop:
> > +    if (avctx->codec_id == AV_CODEC_ID_PNG &&
> > +        avctx->skip_frame == AVDISCARD_ALL) {
> > +        av_frame_set_metadata(p, metadata);
> > +        return 0;
> > +    }
> >  
> >      if (s->bits_per_pixel <= 4)
> >          handle_small_bpp(s, p);
> > @@ -1278,6 +1306,12 @@ static int decode_frame_png(AVCodecContext *avctx,
> >      if ((ret = decode_frame_common(avctx, s, p, avpkt)) < 0)
> >          goto the_end;
> >  
> > +    if (avctx->skip_frame == AVDISCARD_ALL) {
> > +        *got_frame = 0;
> > +        ret = bytestream2_tell(&s->gb);
> > +        goto the_end;
> > +    }
> > +
> >      if ((ret = av_frame_ref(data, s->picture.f)) < 0)
> >          return ret;
> >  
> > -- 
> > 2.6.1
> > 
> 
> Patch updated, the SAR is not discarded anymore.
> 
> Matthieu

>  pngdec.c |   39 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> eddfb042e2653025b37f9deacc0357ac3e5e5148  0001-lavc-pngdec-honor-skip_frame-option.patch
> From ca6362457eb27e623eadcadb0e33a84ea461180f Mon Sep 17 00:00:00 2001
> From: Matthieu Bouron <matthieu.bouron at stupeflix.com>
> Date: Fri, 9 Oct 2015 15:14:11 +0200
> Subject: [PATCH 1/3] lavc/pngdec: honor skip_frame option
> 
> ---
>  libavcodec/pngdec.c | 39 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
> index 4cfdc58..cb99dbe 100644
> --- a/libavcodec/pngdec.c
> +++ b/libavcodec/pngdec.c
> @@ -1087,6 +1087,13 @@ static int decode_frame_common(AVCodecContext *avctx, PNGDecContext *s,
>      for (;;) {
>          length = bytestream2_get_bytes_left(&s->gb);
>          if (length <= 0) {
> +
> +            if (avctx->codec_id == AV_CODEC_ID_PNG &&
> +                avctx->skip_frame == AVDISCARD_ALL) {
> +                av_frame_set_metadata(p, metadata);
> +                return 0;
> +            }
> +
>              if (CONFIG_APNG_DECODER && avctx->codec_id == AV_CODEC_ID_APNG && length == 0) {
>                  if (!(s->state & PNG_IDAT))
>                      return 0;
> @@ -1114,6 +1121,27 @@ static int decode_frame_common(AVCodecContext *avctx, PNGDecContext *s,
>                  ((tag >> 8) & 0xff),
>                  ((tag >> 16) & 0xff),
>                  ((tag >> 24) & 0xff), length);
> +
> +        if (avctx->codec_id == AV_CODEC_ID_PNG &&
> +            avctx->skip_frame == AVDISCARD_ALL) {

> +            int i, found = 0;
> +            static const int tags[] = {
> +                MKTAG('I', 'H', 'D', 'R'),
> +                MKTAG('p', 'H', 'Y', 's'),
> +                MKTAG('t', 'E', 'X', 't'),
> +                MKTAG('I', 'D', 'A', 'T'),
> +            };
> +            for (i = 0; i < FF_ARRAY_ELEMS(tags); i++) {
> +                if (tag == tags[i]) {
> +                    found = 1;
> +                    break;
> +                }
> +            }
> +            if (!found) {
> +                goto skip_tag;
> +            }

as sugested for jpeg, i think this too would be simpler as a switch
the rest of the patch LGTM

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
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