On Tue, Nov 14, 2017 at 08:38:51PM -0800, Aman Gupta wrote:
> On Tue, Nov 14, 2017 at 4:01 PM Michael Niedermayer <mich...@niedermayer.cc>
> wrote:
>
> > On Tue, Nov 14, 2017 at 10:04:02AM -0800, Aman Gupta wrote:
> > > From: Aman Gupta <a...@tmm1.net>
> > >
> > > ---
> > > libavcodec/mpeg12dec.c | 20 ++++++++++++++------
> > > 1 file changed, 14 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
> > > index 82bb1286ff..2c96dfa638 100644
> > > --- a/libavcodec/mpeg12dec.c
> > > +++ b/libavcodec/mpeg12dec.c
> > > @@ -54,6 +54,7 @@ typedef struct Mpeg1Context {
> > > int mpeg_enc_ctx_allocated; /* true if decoding context allocated */
> > > int repeat_field; /* true if we must repeat the field */
> > > AVPanScan pan_scan; /* some temporary storage for the
> > panscan */
> > > + int has_pan_scan;
> > > AVStereo3D stereo3d;
> > > int has_stereo3d;
> > > uint8_t *a53_caption;
> > > @@ -1458,6 +1459,7 @@ static void
> > > mpeg_decode_sequence_display_extension(Mpeg1Context
> > *s1)
> > >
> > > s1->pan_scan.width = 16 * w;
> > > s1->pan_scan.height = 16 * h;
> > > + s1->has_pan_scan = 1;
> > >
> > > if (s->avctx->debug & FF_DEBUG_PICT_INFO)
> > > av_log(s->avctx, AV_LOG_DEBUG, "sde w:%d, h:%d\n", w, h);
> > > @@ -1489,6 +1491,8 @@ static void
> > > mpeg_decode_picture_display_extension(Mpeg1Context
> > *s1)
> > > skip_bits(&s->gb, 1); // marker
> > > }
> > >
> > > + s1->has_pan_scan = 1;
> > > +
> > > if (s->avctx->debug & FF_DEBUG_PICT_INFO)
> > > av_log(s->avctx, AV_LOG_DEBUG,
> > > "pde (%"PRId16",%"PRId16") (%"PRId16",%"PRId16")
> > (%"PRId16",%"PRId16")\n",
> > > @@ -1621,12 +1625,16 @@ static int mpeg_field_start(MpegEncContext *s,
> > const uint8_t *buf, int buf_size)
> > > }
> > > }
> > >
> > > - pan_scan = av_frame_new_side_data(s->current_picture_ptr->f,
> > > - AV_FRAME_DATA_PANSCAN,
> > > - sizeof(s1->pan_scan));
> > > - if (!pan_scan)
> > > - return AVERROR(ENOMEM);
> > > - memcpy(pan_scan->data, &s1->pan_scan, sizeof(s1->pan_scan));
> > > + if (s1->has_pan_scan) {
> > > + pan_scan = av_frame_new_side_data(s->
> > current_picture_ptr->f,
> > > + AV_FRAME_DATA_PANSCAN,
> > > + sizeof(s1->pan_scan));
> > > + if (!pan_scan)
> > > + return AVERROR(ENOMEM);
> > > +
> > > + memcpy(pan_scan->data, &s1->pan_scan, sizeof(s1->pan_scan));
> > > + s1->has_pan_scan = 0;
> >
> > the mpeg2 spec says:
> > "In the case that a given picture does not have
> > a
> > picture_display_extension() then the most recently decoded frame
> > centre
> > offset shall be used."
> >
> > "Following a sequence_header() the value zero shall be used for all
> > frame
> > centre offsets until a picture_display_extension() defines non-zero
> > values."
> >
> > I dont think its a good idea to ommit the "most recently decoded
> > frame centre" on the subset of AVFrames which do not explicitly store
> > it. That would make it hard for applications which want to access this,
> > an application would have to keep track of the last one as well as
> > where sequence headers occured
>
>
> Sorry, my mistake.
>
> Would the patch make sense if I removed the "has_pan_scan = 0" reset? Or isi think so, yes > it better just to always include PANSCAN side data to make it easier for > API consumers. > > Aman [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Good people do not need laws to tell them to act responsibly, while bad people will find a way around the laws. -- Plato
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