2019-01-21 21:47 GMT+01:00, James Almer <jamr...@gmail.com>:
> On 1/21/2019 4:09 PM, FeRD (Frank Dana) wrote:
>> The RSHIFT macro in libavutil/common.h does not actually perform
>> a bitwise right-shift, but rather a rounded version of the same
>> operation, as is noted by a comment above the macro. The rounded
>> divsion macro on the very next line is named ROUNDED_DIV, which
>> seems far more clear.
>>
>> This patch renames RSHIFT to ROUNDED_RSHIFT, then updates all
>> uses of the macro to use the new name. (These are all located
>> in three codec files under libavcodec/.)
>>
>> Signed-off-by: FeRD (Frank Dana) <ferd...@gmail.com>
>> ---
>> libavcodec/mpeg4videodec.c | 4 ++--
>> libavcodec/vp3.c | 16 ++++++++--------
>> libavcodec/vp56.c | 4 ++--
>> libavutil/common.h | 2 +-
>> 4 files changed, 13 insertions(+), 13 deletions(-)
>>
>> diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
>> index f44ee76bd4..5d63ba12ba 100644
>> --- a/libavcodec/mpeg4videodec.c
>> +++ b/libavcodec/mpeg4videodec.c
>> @@ -601,7 +601,7 @@ static inline int get_amv(Mpeg4DecContext *ctx, int n)
>> if (ctx->divx_version == 500 && ctx->divx_build == 413 && a >=
>> s->quarter_sample)
>> sum = s->sprite_offset[0][n] / (1 << (a -
>> s->quarter_sample));
>> else
>> - sum = RSHIFT(s->sprite_offset[0][n] * (1 <<
>> s->quarter_sample), a);
>> + sum = ROUNDED_RSHIFT(s->sprite_offset[0][n] * (1 <<
>> s->quarter_sample), a);
>> } else {
>> dx = s->sprite_delta[n][0];
>> dy = s->sprite_delta[n][1];
>> @@ -623,7 +623,7 @@ static inline int get_amv(Mpeg4DecContext *ctx, int n)
>> v += dx;
>> }
>> }
>> - sum = RSHIFT(sum, a + 8 - s->quarter_sample);
>> + sum = ROUNDED_RSHIFT(sum, a + 8 - s->quarter_sample);
>> }
>>
>> if (sum < -len)
>> diff --git a/libavcodec/vp3.c b/libavcodec/vp3.c
>> index a5d8c2ed0b..13b3d6e22a 100644
>> --- a/libavcodec/vp3.c
>> +++ b/libavcodec/vp3.c
>> @@ -861,10 +861,10 @@ static int unpack_vectors(Vp3DecodeContext *s,
>> GetBitContext *gb)
>>
>> if (s->chroma_y_shift) {
>> if (s->macroblock_coding[current_macroblock] ==
>> MODE_INTER_FOURMV) {
>> - motion_x[0] = RSHIFT(motion_x[0] + motion_x[1] +
>> - motion_x[2] + motion_x[3],
>> 2);
>> - motion_y[0] = RSHIFT(motion_y[0] + motion_y[1] +
>> - motion_y[2] + motion_y[3],
>> 2);
>> + motion_x[0] = ROUNDED_RSHIFT(motion_x[0] +
>> motion_x[1] +
>> + motion_x[2] +
>> motion_x[3], 2);
>> + motion_y[0] = ROUNDED_RSHIFT(motion_y[0] +
>> motion_y[1] +
>> + motion_y[2] +
>> motion_y[3], 2);
>> }
>> motion_x[0] = (motion_x[0] >> 1) | (motion_x[0] & 1);
>> motion_y[0] = (motion_y[0] >> 1) | (motion_y[0] & 1);
>> @@ -873,10 +873,10 @@ static int unpack_vectors(Vp3DecodeContext *s,
>> GetBitContext *gb)
>> s->motion_val[1][frag][1] = motion_y[0];
>> } else if (s->chroma_x_shift) {
>> if (s->macroblock_coding[current_macroblock] ==
>> MODE_INTER_FOURMV) {
>> - motion_x[0] = RSHIFT(motion_x[0] + motion_x[1],
>> 1);
>> - motion_y[0] = RSHIFT(motion_y[0] + motion_y[1],
>> 1);
>> - motion_x[1] = RSHIFT(motion_x[2] + motion_x[3],
>> 1);
>> - motion_y[1] = RSHIFT(motion_y[2] + motion_y[3],
>> 1);
>> + motion_x[0] = ROUNDED_RSHIFT(motion_x[0] +
>> motion_x[1], 1);
>> + motion_y[0] = ROUNDED_RSHIFT(motion_y[0] +
>> motion_y[1], 1);
>> + motion_x[1] = ROUNDED_RSHIFT(motion_x[2] +
>> motion_x[3], 1);
>> + motion_y[1] = ROUNDED_RSHIFT(motion_y[2] +
>> motion_y[3], 1);
>> } else {
>> motion_x[1] = motion_x[0];
>> motion_y[1] = motion_y[0];
>> diff --git a/libavcodec/vp56.c b/libavcodec/vp56.c
>> index b69fe6c176..9359b48bc6 100644
>> --- a/libavcodec/vp56.c
>> +++ b/libavcodec/vp56.c
>> @@ -197,8 +197,8 @@ static void vp56_decode_4mv(VP56Context *s, int row,
>> int col)
>>
>> /* chroma vectors are average luma vectors */
>> if (s->avctx->codec->id == AV_CODEC_ID_VP5) {
>> - s->mv[4].x = s->mv[5].x = RSHIFT(mv.x,2);
>> - s->mv[4].y = s->mv[5].y = RSHIFT(mv.y,2);
>> + s->mv[4].x = s->mv[5].x = ROUNDED_RSHIFT(mv.x,2);
>> + s->mv[4].y = s->mv[5].y = ROUNDED_RSHIFT(mv.y,2);
>> } else {
>> s->mv[4] = s->mv[5] = (VP56mv) {mv.x/4, mv.y/4};
>> }
>> diff --git a/libavutil/common.h b/libavutil/common.h
>> index 8db0291170..0bff7f8f72 100644
>> --- a/libavutil/common.h
>> +++ b/libavutil/common.h
>> @@ -51,7 +51,7 @@
>> #endif
>>
>> //rounded division & shift
>> -#define RSHIFT(a,b) ((a) > 0 ? ((a) + ((1<<(b))>>1))>>(b) : ((a) +
>> ((1<<(b))>>1)-1)>>(b))
>> +#define ROUNDED_RSHIFT(a,b) ((a) > 0 ? ((a) + ((1<<(b))>>1))>>(b) : ((a)
>> + ((1<<(b))>>1)-1)>>(b))
>
> common.h is a public installed library, so this would be an API break.
>
> There's also no good way to deprecate a define and replace it with
> another while informing the library user, so for something purely
> cosmetic like this i don't think it's worth the trouble.
I wonder if we should change all macros that do not start with AV/FF
at the next version bump, this seems not unreasonable.
Carl Eugen
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