[FFmpeg-devel] [PATCH 04/10] avcodec/vc1: Introduce fast path for unescaping bitstream buffer
Ben Avison
bavison at riscosopen.org
Fri Mar 25 20:52:51 EET 2022
Includes a checkasm test.
Signed-off-by: Ben Avison <bavison at riscosopen.org>
---
libavcodec/vc1dec.c | 20 +++++++-------
libavcodec/vc1dsp.c | 2 ++
libavcodec/vc1dsp.h | 3 +++
tests/checkasm/vc1dsp.c | 59 +++++++++++++++++++++++++++++++++++++++++
4 files changed, 74 insertions(+), 10 deletions(-)
diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
index 1c92b9d401..6a30b5b664 100644
--- a/libavcodec/vc1dec.c
+++ b/libavcodec/vc1dec.c
@@ -490,7 +490,7 @@ 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:
@@ -680,7 +680,7 @@ 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;
@@ -697,8 +697,8 @@ 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;
@@ -709,7 +709,7 @@ 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;
@@ -726,8 +726,8 @@ 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);
@@ -761,7 +761,7 @@ 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;
@@ -770,9 +770,9 @@ 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{
diff --git a/libavcodec/vc1dsp.c b/libavcodec/vc1dsp.c
index a29b91bf3d..11d493f002 100644
--- a/libavcodec/vc1dsp.c
+++ b/libavcodec/vc1dsp.c
@@ -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, int 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);
diff --git a/libavcodec/vc1dsp.h b/libavcodec/vc1dsp.h
index c6443acb20..8be1198071 100644
--- a/libavcodec/vc1dsp.h
+++ b/libavcodec/vc1dsp.h
@@ -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);
diff --git a/tests/checkasm/vc1dsp.c b/tests/checkasm/vc1dsp.c
index 0823ccad31..0ab5892403 100644
--- a/tests/checkasm/vc1dsp.c
+++ b/tests/checkasm/vc1dsp.c
@@ -286,6 +286,20 @@ static matrix *generate_inverse_quantized_transform_coefficients(size_t width, s
} \
} while (0)
+#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, len0)) \
+ fail(); \
+ } \
+ } while (0)
+
void checkasm_check_vc1dsp(void)
{
/* Inverse transform input coefficients are stored in a 16-bit buffer
@@ -309,6 +323,14 @@ void checkasm_check_vc1dsp(void)
LOCAL_ALIGNED_4(uint8_t, filter_buf0, [24 * 24]);
LOCAL_ALIGNED_4(uint8_t, filter_buf1, [24 * 24]);
+ /* 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);
@@ -349,4 +371,41 @@ void checkasm_check_vc1dsp(void)
CHECK_LOOP_FILTER(vc1_h_loop_filter16);
report("loop_filter");
+
+ 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);
+ }
+
+ report("unescape_buffer");
}
--
2.25.1
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