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avcodec/vc1: Introduce fast path for unescaping bitstream buffer 

Includes a checkasm test.

Signed-off-by: Ben Avison <bavison@riscosopen.org>
Signed-off-by: Martin Storsjö <martin@martin.st>
This commit is contained in:
Ben Avison 2022-03-31 18:23:45 +01:00 committed by Martin Storsjö
parent bd3615a81a
commit 2e26847780
4 changed files with 82 additions and 10 deletions
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20
libavcodec/vc1dec.c
View File

@ -491,7 +491,7 @@ static av_cold int vc1_decode_init(AVCodecContext *avctx)
size = next - start - 4;
if (size <= 0)
continue;
buf2_size = vc1_unescape_buffer(start + 4, size, buf2);
buf2_size = v->vc1dsp.vc1_unescape_buffer(start + 4, size, buf2);
init_get_bits(&gb, buf2, buf2_size * 8);
switch (AV_RB32(start)) {
case VC1_CODE_SEQHDR:
@ -681,7 +681,7 @@ static int vc1_decode_frame(AVCodecContext *avctx, void *data,
case VC1_CODE_FRAME:
if (avctx->hwaccel)
buf_start = start;
buf_size2 = vc1_unescape_buffer(start + 4, size, buf2);
buf_size2 = v->vc1dsp.vc1_unescape_buffer(start + 4, size, buf2);
break;
case VC1_CODE_FIELD: {
int buf_size3;
@ -698,8 +698,8 @@ static int vc1_decode_frame(AVCodecContext *avctx, void *data,
ret = AVERROR(ENOMEM);
goto err;
}
buf_size3 = vc1_unescape_buffer(start + 4, size,
slices[n_slices].buf);
buf_size3 = v->vc1dsp.vc1_unescape_buffer(start + 4, size,
slices[n_slices].buf);
init_get_bits(&slices[n_slices].gb, slices[n_slices].buf,
buf_size3 << 3);
slices[n_slices].mby_start = avctx->coded_height + 31 >> 5;
@ -710,7 +710,7 @@ static int vc1_decode_frame(AVCodecContext *avctx, void *data,
break;
}
case VC1_CODE_ENTRYPOINT: /* it should be before frame data */
buf_size2 = vc1_unescape_buffer(start + 4, size, buf2);
buf_size2 = v->vc1dsp.vc1_unescape_buffer(start + 4, size, buf2);
init_get_bits(&s->gb, buf2, buf_size2 * 8);
ff_vc1_decode_entry_point(avctx, v, &s->gb);
break;
@ -727,8 +727,8 @@ static int vc1_decode_frame(AVCodecContext *avctx, void *data,
ret = AVERROR(ENOMEM);
goto err;
}
buf_size3 = vc1_unescape_buffer(start + 4, size,
slices[n_slices].buf);
buf_size3 = v->vc1dsp.vc1_unescape_buffer(start + 4, size,
slices[n_slices].buf);
init_get_bits(&slices[n_slices].gb, slices[n_slices].buf,
buf_size3 << 3);
slices[n_slices].mby_start = get_bits(&slices[n_slices].gb, 9);
@ -762,7 +762,7 @@ static int vc1_decode_frame(AVCodecContext *avctx, void *data,
ret = AVERROR(ENOMEM);
goto err;
}
buf_size3 = vc1_unescape_buffer(divider + 4, buf + buf_size - divider - 4, slices[n_slices].buf);
buf_size3 = v->vc1dsp.vc1_unescape_buffer(divider + 4, buf + buf_size - divider - 4, slices[n_slices].buf);
init_get_bits(&slices[n_slices].gb, slices[n_slices].buf,
buf_size3 << 3);
slices[n_slices].mby_start = s->mb_height + 1 >> 1;
@ -771,9 +771,9 @@ static int vc1_decode_frame(AVCodecContext *avctx, void *data,
n_slices1 = n_slices - 1;
n_slices++;
}
buf_size2 = vc1_unescape_buffer(buf, divider - buf, buf2);
buf_size2 = v->vc1dsp.vc1_unescape_buffer(buf, divider - buf, buf2);
} else {
buf_size2 = vc1_unescape_buffer(buf, buf_size, buf2);
buf_size2 = v->vc1dsp.vc1_unescape_buffer(buf, buf_size, buf2);
}
init_get_bits(&s->gb, buf2, buf_size2*8);
} else{

2
libavcodec/vc1dsp.c
View File

@ -34,6 +34,7 @@
#include "rnd_avg.h"
#include "vc1dsp.h"
#include "startcode.h"
#include "vc1_common.h"
/* Apply overlap transform to horizontal edge */
static void vc1_v_overlap_c(uint8_t *src, ptrdiff_t stride)
@ -1030,6 +1031,7 @@ av_cold void ff_vc1dsp_init(VC1DSPContext *dsp)
#endif /* CONFIG_WMV3IMAGE_DECODER || CONFIG_VC1IMAGE_DECODER */
dsp->startcode_find_candidate = ff_startcode_find_candidate_c;
dsp->vc1_unescape_buffer = vc1_unescape_buffer;
if (ARCH_AARCH64)
ff_vc1dsp_init_aarch64(dsp);

3
libavcodec/vc1dsp.h
View File

@ -80,6 +80,9 @@ typedef struct VC1DSPContext {
* one or more further zero bytes and a one byte.
*/
int (*startcode_find_candidate)(const uint8_t *buf, int size);
/* Copy a buffer, removing startcode emulation escape bytes as we go */
int (*vc1_unescape_buffer)(const uint8_t *src, int size, uint8_t *dst);
} VC1DSPContext;
void ff_vc1dsp_init(VC1DSPContext* c);

67
tests/checkasm/vc1dsp.c
View File

@ -374,6 +374,70 @@ static void check_loop_filter(void)
}
}
#define TEST_UNESCAPE \
do { \
for (int count = 100; count > 0; --count) { \
escaped_offset = rnd() & 7; \
unescaped_offset = rnd() & 7; \
escaped_len = (1u << (rnd() % 8) + 3) - (rnd() & 7); \
RANDOMIZE_BUFFER8(unescaped, UNESCAPE_BUF_SIZE); \
len0 = call_ref(escaped0 + escaped_offset, escaped_len, unescaped0 + unescaped_offset); \
len1 = call_new(escaped1 + escaped_offset, escaped_len, unescaped1 + unescaped_offset); \
if (len0 != len1 || memcmp(unescaped0, unescaped1, UNESCAPE_BUF_SIZE)) \
fail(); \
} \
} while (0)
static void check_unescape(void)
{
/* This appears to be a typical length of buffer in use */
#define LOG2_UNESCAPE_BUF_SIZE 17
#define UNESCAPE_BUF_SIZE (1u<<LOG2_UNESCAPE_BUF_SIZE)
LOCAL_ALIGNED_8(uint8_t, escaped0, [UNESCAPE_BUF_SIZE]);
LOCAL_ALIGNED_8(uint8_t, escaped1, [UNESCAPE_BUF_SIZE]);
LOCAL_ALIGNED_8(uint8_t, unescaped0, [UNESCAPE_BUF_SIZE]);
LOCAL_ALIGNED_8(uint8_t, unescaped1, [UNESCAPE_BUF_SIZE]);
VC1DSPContext h;
ff_vc1dsp_init(&h);
if (check_func(h.vc1_unescape_buffer, "vc1dsp.vc1_unescape_buffer")) {
int len0, len1, escaped_offset, unescaped_offset, escaped_len;
declare_func_emms(AV_CPU_FLAG_MMX, int, const uint8_t *, int, uint8_t *);
/* Test data which consists of escapes sequences packed as tightly as possible */
for (int x = 0; x < UNESCAPE_BUF_SIZE; ++x)
escaped1[x] = escaped0[x] = 3 * (x % 3 == 0);
TEST_UNESCAPE;
/* Test random data */
RANDOMIZE_BUFFER8(escaped, UNESCAPE_BUF_SIZE);
TEST_UNESCAPE;
/* Test data with escape sequences at random intervals */
for (int x = 0; x <= UNESCAPE_BUF_SIZE - 4;) {
int gap, gap_msb;
escaped1[x+0] = escaped0[x+0] = 0;
escaped1[x+1] = escaped0[x+1] = 0;
escaped1[x+2] = escaped0[x+2] = 3;
escaped1[x+3] = escaped0[x+3] = rnd() & 3;
gap_msb = 2u << (rnd() % 8);
gap = (rnd() &~ -gap_msb) | gap_msb;
x += gap;
}
TEST_UNESCAPE;
/* Test data which is known to contain no escape sequences */
memset(escaped0, 0xFF, UNESCAPE_BUF_SIZE);
memset(escaped1, 0xFF, UNESCAPE_BUF_SIZE);
TEST_UNESCAPE;
/* Benchmark the no-escape-sequences case */
bench_new(escaped1, UNESCAPE_BUF_SIZE, unescaped1);
}
}
void checkasm_check_vc1dsp(void)
{
check_inv_trans_inplace();
@ -382,4 +446,7 @@ void checkasm_check_vc1dsp(void)
check_loop_filter();
report("loop_filter");
check_unescape();
report("unescape_buffer");
}