On Wed, Sep 27, 2017 at 4:13 PM, wm4 <nfx...@googlemail.com> wrote:
> On Wed, 27 Sep 2017 19:45:23 -0300
> James Almer <jamr...@gmail.com> wrote:
>
> > On 9/27/2017 7:19 PM, Aman Gupta wrote:
> > > From: Aman Gupta <a...@tmm1.net>
> > >
> > > additional changes to hevc patchset, as suggested on-list
> > >
> > > if these look fine, I will squash into previous patchset and push it to
> > > master.
> > > ---
> > > libavcodec/videotoolbox.c | 27 +++++++++------------------
> > > 1 file changed, 9 insertions(+), 18 deletions(-)
> > >
> > > diff --git a/libavcodec/videotoolbox.c b/libavcodec/videotoolbox.c
> > > index 078174cc61..c96200cbdb 100644
> > > --- a/libavcodec/videotoolbox.c
> > > +++ b/libavcodec/videotoolbox.c
> > > @@ -165,10 +165,8 @@ CFDataRef
> > > ff_videotoolbox_hvcc_extradata_create(AVCodecContext
> *avctx)
> > > ptlc.non_packed_constraint_flag << 5 |
> > > ptlc.frame_only_constraint_flag << 4);
> > > AV_W8(p + 7, 0);
> > > - AV_W8(p + 8, 0);
> > > - AV_W8(p + 9, 0);
> > > - AV_W8(p + 10, 0);
> > > - AV_W8(p + 11, 0);
> > > + AV_WB16(p + 8, 0);
> > > + AV_WB16(p + 10, 0);
> >
> > AV_WB32(p + 8, 0)
> >
> > or even AV_WN32(p + 8, 0) since it's 0 and endianness doesn't matter.
>
> IMO it should reflect whatever bitstream elements these are. Ideally,
> we'd have comments about what each element is too.
>
There is already a comment in this section. It's supposed to be 48bits of
flags, but the spec has 44 of those bits defined as 'reserved zero bits'.
/* unsigned int(48) general_constraint_indicator_flags; */
AV_W8(p + 6, ptlc.progressive_source_flag << 7 |
ptlc.interlaced_source_flag << 6 |
ptlc.non_packed_constraint_flag << 5 |
ptlc.frame_only_constraint_flag << 4);
AV_W8(p + 7, 0);
AV_WN32(p + 8, 0);
In hvcc_write (lavf/hevc.c), libavformat uses:
/* unsigned int(48) general_constraint_indicator_flags; */
avio_wb32(pb, hvcc->general_constraint_indicator_flags >> 16);
avio_wb16(pb, hvcc->general_constraint_indicator_flags);
But the PTL parsing code in libavcodec defines the flags individually.
See decode_profile_tier_level (lavc/hevc_ps.c):
ptl->progressive_source_flag = get_bits1(gb);
ptl->interlaced_source_flag = get_bits1(gb);
ptl->non_packed_constraint_flag = get_bits1(gb);
ptl->frame_only_constraint_flag = get_bits1(gb);
skip_bits(gb, 16); // XXX_reserved_zero_44bits[0..15]
skip_bits(gb, 16); // XXX_reserved_zero_44bits[16..31]
skip_bits(gb, 12); // XXX_reserved_zero_44bits[32..43]
Aman
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