Re: [libav-devel] [PATCH 2/5] vc1dec: Invoke edge emulation regardless of MV precision for 1-MV chroma

2012-10-09 Thread Kostya Shishkov 
On Tue, Oct 09, 2012 at 04:38:16PM -0400, Mashiat Sarker Shakkhar wrote:
> This is required due to the way VC-1 handles chroma pull-back which may end
> up causing negative chroma MV for zero luma MV. Edge emulation needs to be
> invoked in such cases.
> 
> This problem only affects chroma Y motion vector.

Ahem, that sentence induces cognitive dissonance:
first you see "chroma Y" and think "why not Cb luma",
then you move further and see it's actually "Y motion vector".
As far as I remember, Y is merely one component of motion vector,
so please reformulate it a bit, like "only affects vertical component of
chroma motion vector" or so.

> ---
>  libavcodec/vc1dec.c |2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
> index 42eb4a5..2683c86 100644
> --- a/libavcodec/vc1dec.c
> +++ b/libavcodec/vc1dec.c
> @@ -430,7 +430,7 @@ static void vc1_mc_1mv(VC1Context *v, int dir)
>  if (v->rangeredfrm || (v->mv_mode == MV_PMODE_INTENSITY_COMP)
>  || s->h_edge_pos < 22 || v_edge_pos < 22
>  || (unsigned)(src_x - s->mspel) > s->h_edge_pos - (mx&3) - 16 - 
> s->mspel * 3
> -|| (unsigned)(src_y - s->mspel) > v_edge_pos- (my&3) - 16 - 
> s->mspel * 3) {
> +|| (unsigned)(src_y - 1)> v_edge_pos- (my&3) - 16 - 3) {
>  uint8_t *uvbuf = s->edge_emu_buffer + 19 * s->linesize;
>  
>  srcY -= s->mspel * (1 + s->linesize);
> -- 

The patch looks OK.
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Re: [libav-devel] [PATCH 2/5] vc1dec: Invoke edge emulation regardless of MV precision for 1-MV chroma

2012-10-09 Thread Ronald S. Bultje 
Hi,

On Tue, Oct 9, 2012 at 4:56 PM, Mashiat Sarker Shakkhar
 wrote:
> On 10/9/2012 7:37 PM, Ronald S. Bultje wrote:
>>
>> Hi,
>>
>> On Tue, Oct 9, 2012 at 1:38 PM, Mashiat Sarker Shakkhar
>>  wrote:
>>>
>>> This is required due to the way VC-1 handles chroma pull-back which may
>>> end
>>> up causing negative chroma MV for zero luma MV. Edge emulation needs to
>>> be
>>> invoked in such cases.
>>>
>>> This problem only affects chroma Y motion vector.
>>> ---
>>>   libavcodec/vc1dec.c |2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
>>> index 42eb4a5..2683c86 100644
>>> --- a/libavcodec/vc1dec.c
>>> +++ b/libavcodec/vc1dec.c
>>> @@ -430,7 +430,7 @@ static void vc1_mc_1mv(VC1Context *v, int dir)
>>>   if (v->rangeredfrm || (v->mv_mode == MV_PMODE_INTENSITY_COMP)
>>>   || s->h_edge_pos < 22 || v_edge_pos < 22
>>>   || (unsigned)(src_x - s->mspel) > s->h_edge_pos - (mx&3) - 16 -
>>> s->mspel * 3
>>> -|| (unsigned)(src_y - s->mspel) > v_edge_pos- (my&3) - 16 -
>>> s->mspel * 3) {
>>> +|| (unsigned)(src_y - 1)> v_edge_pos- (my&3) - 16 -
>>> 3) {
>>
>>
>> I'm slightly curious why this is only the case for the vertical
>> dimension, but not the horizontal. Is that intentional, or an
>> oversight?
>
>
> This thread contains my earlier discussion on a rejected patch which tried
> to fix the same bug:
>
> http://patches.libav.org/patch/26240/

OK so it's not because of pullback per se, but because of field
adjustment, then it makes sense.

Ronald
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Re: [libav-devel] [PATCH 2/5] vc1dec: Invoke edge emulation regardless of MV precision for 1-MV chroma

2012-10-09 Thread Mashiat Sarker Shakkhar 

On 10/9/2012 7:37 PM, Ronald S. Bultje wrote:

Hi,

On Tue, Oct 9, 2012 at 1:38 PM, Mashiat Sarker Shakkhar
 wrote:

This is required due to the way VC-1 handles chroma pull-back which may end
up causing negative chroma MV for zero luma MV. Edge emulation needs to be
invoked in such cases.

This problem only affects chroma Y motion vector.
---
  libavcodec/vc1dec.c |2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
index 42eb4a5..2683c86 100644
--- a/libavcodec/vc1dec.c
+++ b/libavcodec/vc1dec.c
@@ -430,7 +430,7 @@ static void vc1_mc_1mv(VC1Context *v, int dir)
  if (v->rangeredfrm || (v->mv_mode == MV_PMODE_INTENSITY_COMP)
  || s->h_edge_pos < 22 || v_edge_pos < 22
  || (unsigned)(src_x - s->mspel) > s->h_edge_pos - (mx&3) - 16 - 
s->mspel * 3
-|| (unsigned)(src_y - s->mspel) > v_edge_pos- (my&3) - 16 - 
s->mspel * 3) {
+|| (unsigned)(src_y - 1)> v_edge_pos- (my&3) - 16 - 3) {


I'm slightly curious why this is only the case for the vertical
dimension, but not the horizontal. Is that intentional, or an
oversight?


This thread contains my earlier discussion on a rejected patch which 
tried to fix the same bug:


http://patches.libav.org/patch/26240/

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Re: [libav-devel] [PATCH 2/5] vc1dec: Invoke edge emulation regardless of MV precision for 1-MV chroma

2012-10-09 Thread Ronald S. Bultje 
Hi,

On Tue, Oct 9, 2012 at 1:38 PM, Mashiat Sarker Shakkhar
 wrote:
> This is required due to the way VC-1 handles chroma pull-back which may end
> up causing negative chroma MV for zero luma MV. Edge emulation needs to be
> invoked in such cases.
>
> This problem only affects chroma Y motion vector.
> ---
>  libavcodec/vc1dec.c |2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
> index 42eb4a5..2683c86 100644
> --- a/libavcodec/vc1dec.c
> +++ b/libavcodec/vc1dec.c
> @@ -430,7 +430,7 @@ static void vc1_mc_1mv(VC1Context *v, int dir)
>  if (v->rangeredfrm || (v->mv_mode == MV_PMODE_INTENSITY_COMP)
>  || s->h_edge_pos < 22 || v_edge_pos < 22
>  || (unsigned)(src_x - s->mspel) > s->h_edge_pos - (mx&3) - 16 - 
> s->mspel * 3
> -|| (unsigned)(src_y - s->mspel) > v_edge_pos- (my&3) - 16 - 
> s->mspel * 3) {
> +|| (unsigned)(src_y - 1)> v_edge_pos- (my&3) - 16 - 3) {

I'm slightly curious why this is only the case for the vertical
dimension, but not the horizontal. Is that intentional, or an
oversight?

Ronald
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[libav-devel] [PATCH 2/5] vc1dec: Invoke edge emulation regardless of MV precision for 1-MV chroma

2012-10-09 Thread Mashiat Sarker Shakkhar 
This is required due to the way VC-1 handles chroma pull-back which may end
up causing negative chroma MV for zero luma MV. Edge emulation needs to be
invoked in such cases.

This problem only affects chroma Y motion vector.
---
 libavcodec/vc1dec.c |2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
index 42eb4a5..2683c86 100644
--- a/libavcodec/vc1dec.c
+++ b/libavcodec/vc1dec.c
@@ -430,7 +430,7 @@ static void vc1_mc_1mv(VC1Context *v, int dir)
 if (v->rangeredfrm || (v->mv_mode == MV_PMODE_INTENSITY_COMP)
 || s->h_edge_pos < 22 || v_edge_pos < 22
 || (unsigned)(src_x - s->mspel) > s->h_edge_pos - (mx&3) - 16 - 
s->mspel * 3
-|| (unsigned)(src_y - s->mspel) > v_edge_pos- (my&3) - 16 - 
s->mspel * 3) {
+|| (unsigned)(src_y - 1)> v_edge_pos- (my&3) - 16 - 3) {
 uint8_t *uvbuf = s->edge_emu_buffer + 19 * s->linesize;
 
 srcY -= s->mspel * (1 + s->linesize);
-- 
1.7.9.5

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