[FFmpeg-devel] [PATCH 3/9] avcodecc/asvdec: Avoid reversing input data twice
Andreas Rheinhardt
andreas.rheinhardt at gmail.com
Tue Oct 13 12:10:11 EEST 2020
Up until now the ASV2 decoder used an ordinary big-endian bitreader to
read data actually destined for a little-endian bitreader; this is done
by reversing the whole input packet bitwise, using the big-endian
bigreader and reversing (and shifting) the result again. This commit
stops this and instead uses a little-endian bitreader directly.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
libavcodec/asvdec.c | 77 ++++++++++++++++++++++++++-------------------
1 file changed, 44 insertions(+), 33 deletions(-)
diff --git a/libavcodec/asvdec.c b/libavcodec/asvdec.c
index 6198188fc5..78e53b6402 100644
--- a/libavcodec/asvdec.c
+++ b/libavcodec/asvdec.c
@@ -31,7 +31,6 @@
#include "blockdsp.h"
#include "idctdsp.h"
#include "internal.h"
-#include "mathops.h"
#include "mpeg12data.h"
#define CCP_VLC_BITS 5
@@ -56,27 +55,24 @@ static av_cold void init_vlcs(ASV1Context *a)
INIT_VLC_STATIC(&ccp_vlc, CCP_VLC_BITS, 17,
&ff_asv_ccp_tab[0][1], 2, 1,
&ff_asv_ccp_tab[0][0], 2, 1, 32);
- INIT_VLC_STATIC(&dc_ccp_vlc, DC_CCP_VLC_BITS, 8,
- &ff_asv_dc_ccp_tab[0][1], 2, 1,
- &ff_asv_dc_ccp_tab[0][0], 2, 1, 16);
- INIT_VLC_STATIC(&ac_ccp_vlc, AC_CCP_VLC_BITS, 16,
- &ff_asv_ac_ccp_tab[0][1], 2, 1,
- &ff_asv_ac_ccp_tab[0][0], 2, 1, 64);
+ INIT_CUSTOM_VLC_STATIC(&dc_ccp_vlc, DC_CCP_VLC_BITS, 8,
+ &ff_asv_dc_ccp_tab[0][1], 2, 1,
+ &ff_asv_dc_ccp_tab[0][0], 2, 1,
+ INIT_VLC_OUTPUT_LE, 16);
+ INIT_CUSTOM_VLC_STATIC(&ac_ccp_vlc, AC_CCP_VLC_BITS, 16,
+ &ff_asv_ac_ccp_tab[0][1], 2, 1,
+ &ff_asv_ac_ccp_tab[0][0], 2, 1,
+ INIT_VLC_OUTPUT_LE, 64);
INIT_VLC_STATIC(&level_vlc, ASV1_LEVEL_VLC_BITS, 7,
&ff_asv_level_tab[0][1], 2, 1,
&ff_asv_level_tab[0][0], 2, 1, 16);
- INIT_VLC_STATIC(&asv2_level_vlc, ASV2_LEVEL_VLC_BITS, 63,
- &ff_asv2_level_tab[0][1], 2, 1,
- &ff_asv2_level_tab[0][0], 2, 1, 1024);
+ INIT_CUSTOM_VLC_STATIC(&asv2_level_vlc, ASV2_LEVEL_VLC_BITS, 63,
+ &ff_asv2_level_tab[0][1], 2, 1,
+ &ff_asv2_level_tab[0][0], 2, 1,
+ INIT_VLC_OUTPUT_LE, 1024);
}
}
-// FIXME write a reversed bitstream reader to avoid the double reverse
-static inline int asv2_get_bits(GetBitContext *gb, int n)
-{
- return ff_reverse[get_bits(gb, n) << (8 - n)];
-}
-
static inline int asv1_get_level(GetBitContext *gb)
{
int code = get_vlc2(gb, level_vlc.table, ASV1_LEVEL_VLC_BITS, 1);
@@ -87,12 +83,31 @@ static inline int asv1_get_level(GetBitContext *gb)
return code - 3;
}
+// get_vlc2() is big-endian in this file
+static inline int asv2_get_vlc2(GetBitContext *gb, VLC_TYPE (*table)[2], int bits)
+{
+ unsigned int index;
+ int code, n;
+
+ OPEN_READER(re, gb);
+ UPDATE_CACHE_LE(re, gb);
+
+ index = SHOW_UBITS_LE(re, gb, bits);
+ code = table[index][0];
+ n = table[index][1];
+ LAST_SKIP_BITS(re, gb, n);
+
+ CLOSE_READER(re, gb);
+
+ return code;
+}
+
static inline int asv2_get_level(GetBitContext *gb)
{
- int code = get_vlc2(gb, asv2_level_vlc.table, ASV2_LEVEL_VLC_BITS, 1);
+ int code = asv2_get_vlc2(gb, asv2_level_vlc.table, ASV2_LEVEL_VLC_BITS);
if (code == 31)
- return (int8_t) asv2_get_bits(gb, 8);
+ return (int8_t) get_bits_le(gb, 8);
else
return code - 31;
}
@@ -132,11 +147,11 @@ static inline int asv2_decode_block(ASV1Context *a, int16_t block[64])
{
int i, count, ccp;
- count = asv2_get_bits(&a->gb, 4);
+ count = get_bits_le(&a->gb, 4);
- block[0] = 8 * asv2_get_bits(&a->gb, 8);
+ block[0] = 8 * get_bits_le(&a->gb, 8);
- ccp = get_vlc2(&a->gb, dc_ccp_vlc.table, DC_CCP_VLC_BITS, 1);
+ ccp = asv2_get_vlc2(&a->gb, dc_ccp_vlc.table, DC_CCP_VLC_BITS);
if (ccp) {
if (ccp & 4)
block[a->scantable.permutated[1]] = (asv2_get_level(&a->gb) * a->intra_matrix[1]) >> 4;
@@ -147,7 +162,7 @@ static inline int asv2_decode_block(ASV1Context *a, int16_t block[64])
}
for (i = 1; i < count + 1; i++) {
- const int ccp = get_vlc2(&a->gb, ac_ccp_vlc.table, AC_CCP_VLC_BITS, 1);
+ const int ccp = asv2_get_vlc2(&a->gb, ac_ccp_vlc.table, AC_CCP_VLC_BITS);
if (ccp) {
if (ccp & 8)
@@ -221,21 +236,18 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
p->pict_type = AV_PICTURE_TYPE_I;
p->key_frame = 1;
- av_fast_padded_malloc(&a->bitstream_buffer, &a->bitstream_buffer_size,
- buf_size);
- if (!a->bitstream_buffer)
- return AVERROR(ENOMEM);
-
if (avctx->codec_id == AV_CODEC_ID_ASV1) {
+ av_fast_padded_malloc(&a->bitstream_buffer, &a->bitstream_buffer_size,
+ buf_size);
+ if (!a->bitstream_buffer)
+ return AVERROR(ENOMEM);
+
a->bbdsp.bswap_buf((uint32_t *) a->bitstream_buffer,
(const uint32_t *) buf, buf_size / 4);
+ ret = init_get_bits8(&a->gb, a->bitstream_buffer, buf_size);
} else {
- int i;
- for (i = 0; i < buf_size; i++)
- a->bitstream_buffer[i] = ff_reverse[buf[i]];
+ ret = init_get_bits8_le(&a->gb, buf, buf_size);
}
-
- ret = init_get_bits8(&a->gb, a->bitstream_buffer, buf_size);
if (ret < 0)
return ret;
@@ -342,7 +354,6 @@ AVCodec ff_asv2_decoder = {
.id = AV_CODEC_ID_ASV2,
.priv_data_size = sizeof(ASV1Context),
.init = decode_init,
- .close = decode_end,
.decode = decode_frame,
.capabilities = AV_CODEC_CAP_DR1,
};
--
2.25.1
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