[FFmpeg-devel] [PATCH 2/4] h264dec: be more explicit in handling container cropping

[Michael Niedermayer]

On Wed, May 10, 2017 at 11:06:52PM -0300, James Almer wrote:
> On 5/10/2017 9:55 PM, Michael Niedermayer wrote:
> > On Wed, May 10, 2017 at 10:41:30AM -0300, James Almer wrote:
> >> On 5/9/2017 11:56 PM, Michael Niedermayer wrote:
> >>> On Mon, May 08, 2017 at 03:46:23PM -0300, James Almer wrote:
> >>>> From: Anton Khirnov <anton at khirnov.net>
> >>>>
> >>>> The current condition can trigger in cases where it shouldn't, with
> >>>> unexpected results.
> >>>> Make sure that:
> >>>> - container cropping is really based on the original dimensions from the
> >>>>   caller
> >>>> - those dimenions are discarded on size change
> >>>>
> >>>> The code is still quite hacky and eventually should be deprecated and
> >>>> removed, with the decision about which cropping is used delegated to the
> >>>> caller.
> >>>> ---
> >>>> This merges commit 4fded0480f20f4d7ca5e776a85574de34dfead14 from libav
> >>>>
> >>>>  libavcodec/h264_slice.c | 20 +++++++++++++-------
> >>>>  libavcodec/h264dec.c    |  3 +++
> >>>>  libavcodec/h264dec.h    |  5 +++++
> >>>>  3 files changed, 21 insertions(+), 7 deletions(-)
> >>>>
> >>>> diff --git a/libavcodec/h264_slice.c b/libavcodec/h264_slice.c
> >>>> index acf6a73f60..a7916e09ce 100644
> >>>> --- a/libavcodec/h264_slice.c
> >>>> +++ b/libavcodec/h264_slice.c
> >>>> @@ -378,6 +378,8 @@ int ff_h264_update_thread_context(AVCodecContext *dst,
> >>>>      h->avctx->coded_width   = h1->avctx->coded_width;
> >>>>      h->avctx->width         = h1->avctx->width;
> >>>>      h->avctx->height        = h1->avctx->height;
> >>>> +    h->width_from_caller    = h1->width_from_caller;
> >>>> +    h->height_from_caller   = h1->height_from_caller;
> >>>>      h->coded_picture_number = h1->coded_picture_number;
> >>>>      h->first_field          = h1->first_field;
> >>>>      h->picture_structure    = h1->picture_structure;
> >>>
> >>>> @@ -874,13 +876,17 @@ static int init_dimensions(H264Context *h)
> >>>>      av_assert0(sps->crop_top + sps->crop_bottom < (unsigned)h->height);
> >>>>  
> >>>>      /* handle container cropping */
> >>>> -    if (FFALIGN(h->avctx->width,  16) == FFALIGN(width,  16) &&
> >>>> -        FFALIGN(h->avctx->height, 16) == FFALIGN(height, 16) &&
> >>>> -        h->avctx->width  <= width &&
> >>>> -        h->avctx->height <= height
> >>>> -    ) {
> >>>> -        width  = h->avctx->width;
> >>>> -        height = h->avctx->height;
> >>>> +    if (h->width_from_caller > 0 && h->height_from_caller > 0     &&
> >>>> +        !sps->crop_top && !sps->crop_left                         &&
> >>>> +        FFALIGN(h->width_from_caller,  16) == FFALIGN(width,  16) &&
> >>>> +        FFALIGN(h->height_from_caller, 16) == FFALIGN(height, 16) &&
> >>>> +        h->width_from_caller  <= width &&
> >>>> +        h->height_from_caller <= height) {
> >>>> +        width  = h->width_from_caller;
> >>>> +        height = h->height_from_caller;
> >>>> +    } else {
> >>>> +        h->width_from_caller  = 0;
> >>>> +        h->height_from_caller = 0;
> >>>>      }
> >>>
> >>> With this, seeking in a file could affect if croping is used
> >>> would something break if croping was unaffected by what was priorly
> >>> decoded ?
> >>
> >> I don't know. Do you have a test case where this could break that i can
> >> check?
> > 
> > no, it was just an thought that came to my mind when looking at the
> > code. I dont remember seeing this break anything, it changed some
> > files output though unless these were caused by another patch i had
> > locally
> 
> Could you try to confirm they weren't changed by this patch? Unless i'm
> reading it wrong, this set afaik isn't supposed to change the output of
> the decoder (at least not negatively), as reflected by fate, just move
> the cropping logic to decode.c

I retested, it was
[3/4] h264dec: export cropping information instead of handling it internally
that caused the changes
changes seen are with CVFC1_Sony_C.jsv and tickets/4274/sample.ts

4247 needs "-threads 1  -flags2 showall -ss 7" for showin the
difference, the sony file shows a difference with just plain default
reencoding to avi

Our fate test doesnt change, i guess due to -flags unaligned in it

thx

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

If you think the mosad wants you dead since a long time then you are either
wrong or dead since a long time.
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