[FFmpeg-cvslog] avcodec: add multi vlc reader
Paul B Mahol
git at videolan.org
Thu Sep 7 01:19:25 EEST 2023
ffmpeg | branch: master | Paul B Mahol <onemda at gmail.com> | Sun Aug 27 21:18:46 2023 +0200| [29b9fca4b3ca24ee8d8f951a3afe6daa77089096] | committer: Paul B Mahol
avcodec: add multi vlc reader
Heavily based and inspired by Christophe's cache branches.
Co-Authored-by: Christophe Gisquet
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=29b9fca4b3ca24ee8d8f951a3afe6daa77089096
---
libavcodec/bitstream.h | 2 +
libavcodec/bitstream_template.h | 29 +++++++++
libavcodec/get_bits.h | 10 +++
libavcodec/vlc.c | 137 ++++++++++++++++++++++++++++++++++++++++
libavcodec/vlc.h | 53 ++++++++++++++++
5 files changed, 231 insertions(+)
diff --git a/libavcodec/bitstream.h b/libavcodec/bitstream.h
index b60f0c296d..35b7873b9c 100644
--- a/libavcodec/bitstream.h
+++ b/libavcodec/bitstream.h
@@ -102,6 +102,7 @@
# define bits_decode210 bits_decode210_le
# define bits_apply_sign bits_apply_sign_le
# define bits_read_vlc bits_read_vlc_le
+# define bits_read_vlc_multi bits_read_vlc_multi_le
#elif defined(BITS_DEFAULT_BE)
@@ -130,6 +131,7 @@
# define bits_decode210 bits_decode210_be
# define bits_apply_sign bits_apply_sign_be
# define bits_read_vlc bits_read_vlc_be
+# define bits_read_vlc_multi bits_read_vlc_multi_be
#endif
diff --git a/libavcodec/bitstream_template.h b/libavcodec/bitstream_template.h
index 30bea84add..0308e3a924 100644
--- a/libavcodec/bitstream_template.h
+++ b/libavcodec/bitstream_template.h
@@ -520,6 +520,35 @@ static inline int BS_FUNC(read_vlc)(BSCTX *bc, const VLCElem *table,
return code;
}
+static inline int BS_FUNC(read_vlc_multi)(BSCTX *bc, uint8_t *dst,
+ const VLC_MULTI_ELEM *const Jtable,
+ const VLCElem *const table,
+ const int bits, const int max_depth)
+{
+ unsigned idx = BS_FUNC(peek)(bc, bits);
+ int ret, nb_bits, code, n = Jtable[idx].len;
+ if (Jtable[idx].num) {
+ AV_COPY64U(dst, Jtable[idx].val);
+ ret = Jtable[idx].num;
+ } else {
+ code = table[idx].sym;
+ n = table[idx].len;
+ if (max_depth > 1 && n < 0) {
+ BS_FUNC(priv_skip_remaining)(bc, bits);
+ code = BS_FUNC(priv_set_idx)(bc, code, &n, &nb_bits, table);
+ if (max_depth > 2 && n < 0) {
+ BS_FUNC(priv_skip_remaining)(bc, nb_bits);
+ code = BS_FUNC(priv_set_idx)(bc, code, &n, &nb_bits, table);
+ }
+ }
+ AV_WN16(dst, code);
+ ret = n > 0;
+ }
+ BS_FUNC(priv_skip_remaining)(bc, n);
+
+ return ret;
+}
+
#undef BSCTX
#undef BS_FUNC
#undef BS_JOIN3
diff --git a/libavcodec/get_bits.h b/libavcodec/get_bits.h
index 65dc080ddb..0594e104bb 100644
--- a/libavcodec/get_bits.h
+++ b/libavcodec/get_bits.h
@@ -93,6 +93,7 @@ typedef BitstreamContext GetBitContext;
#define init_get_bits8 bits_init8
#define align_get_bits bits_align
#define get_vlc2 bits_read_vlc
+#define get_vlc_multi bits_read_vlc_multi
#define init_get_bits8_le(s, buffer, byte_size) bits_init8_le((BitstreamContextLE*)s, buffer, byte_size)
#define get_bits_le(s, n) bits_read_le((BitstreamContextLE*)s, n)
@@ -643,6 +644,15 @@ static av_always_inline int get_vlc2(GetBitContext *s, const VLCElem *table,
return code;
}
+static inline int get_vlc_multi(GetBitContext *s, uint8_t *dst,
+ const VLC_MULTI_ELEM *const Jtable,
+ const VLCElem *const table,
+ const int bits, const int max_depth)
+{
+ dst[0] = get_vlc2(s, table, bits, max_depth);
+ return 1;
+}
+
static inline int decode012(GetBitContext *gb)
{
int n;
diff --git a/libavcodec/vlc.c b/libavcodec/vlc.c
index 96f2b28c7e..9656a9472c 100644
--- a/libavcodec/vlc.c
+++ b/libavcodec/vlc.c
@@ -30,6 +30,7 @@
#include "libavutil/avassert.h"
#include "libavutil/error.h"
#include "libavutil/internal.h"
+#include "libavutil/intreadwrite.h"
#include "libavutil/log.h"
#include "libavutil/macros.h"
#include "libavutil/mem.h"
@@ -372,6 +373,142 @@ fail:
return AVERROR_INVALIDDATA;
}
+static void add_level(VLC_MULTI_ELEM *table, const int nb_elems,
+ const int num, const int numbits,
+ const VLCcode *buf,
+ uint32_t curcode, int curlen,
+ int curlimit, int curlevel,
+ const int minlen, const int max,
+ unsigned* levelcnt, VLC_MULTI_ELEM *info)
+{
+ if (nb_elems > 256 && curlevel > 2)
+ return; // No room
+ for (int i = num-1; i > max; i--) {
+ for (int j = 0; j < 2; j++) {
+ int newlimit, sym;
+ int t = j ? i-1 : i;
+ int l = buf[t].bits;
+ uint32_t code;
+
+ sym = buf[t].symbol;
+ if (l > curlimit)
+ return;
+ code = curcode + (buf[t].code >> curlen);
+ newlimit = curlimit - l;
+ l += curlen;
+ if (nb_elems>256) AV_WN16(info->val+2*curlevel, sym);
+ else info->val[curlevel] = sym&0xFF;
+
+ if (curlevel) { // let's not add single entries
+ uint32_t val = code >> (32 - numbits);
+ uint32_t nb = val + (1U << (numbits - l));
+ info->len = l;
+ info->num = curlevel+1;
+ for (; val < nb; val++)
+ AV_COPY64(table+val, info);
+ levelcnt[curlevel-1]++;
+ }
+
+ if (curlevel+1 < VLC_MULTI_MAX_SYMBOLS && newlimit >= minlen) {
+ add_level(table, nb_elems, num, numbits, buf,
+ code, l, newlimit, curlevel+1,
+ minlen, max, levelcnt, info);
+ }
+ }
+ }
+}
+
+static int vlc_multi_gen(VLC_MULTI_ELEM *table, const VLC *single,
+ const int nb_elems, const int nb_codes, const int numbits,
+ VLCcode *buf, void *logctx)
+{
+ int minbits, maxbits, max = nb_codes-1;
+ unsigned count[VLC_MULTI_MAX_SYMBOLS-1] = { 0, };
+ VLC_MULTI_ELEM info = { { 0, }, 0, };
+
+ minbits = buf[nb_codes-1].bits;
+ maxbits = FFMIN(buf[0].bits, numbits);
+
+ while (max >= nb_codes/2) {
+ if (buf[max].bits+minbits > maxbits)
+ break;
+ max--;
+ }
+
+ for (int j = 0; j < 1<<numbits; j++) {
+ table[j].len = single->table[j].len;
+ table[j].num = single->table[j].len > 0 ? 1 : 0;
+ AV_WN16(table[j].val, single->table[j].sym);
+ }
+
+ add_level(table, nb_elems, nb_codes, numbits, buf,
+ 0, 0, numbits, 0, minbits, max, count, &info);
+
+ av_log(NULL, AV_LOG_DEBUG, "Joint: %d/%d/%d/%d/%d codes min=%ubits max=%u\n",
+ count[0], count[1], count[2], count[3], count[4], minbits, max);
+
+ return 0;
+}
+
+int ff_init_vlc_multi_from_lengths(VLC *vlc, VLC_MULTI *multi, int nb_bits, int nb_elems,
+ int nb_codes, const int8_t *lens, int lens_wrap,
+ const void *symbols, int symbols_wrap, int symbols_size,
+ int offset, int flags, void *logctx)
+{
+ VLCcode localbuf[LOCALBUF_ELEMS], *buf = localbuf;
+ uint64_t code;
+ int ret, j, len_max = FFMIN(32, 3 * nb_bits);
+
+ ret = vlc_common_init(vlc, nb_bits, nb_codes, &buf, flags);
+ if (ret < 0)
+ return ret;
+
+ multi->table = av_malloc(sizeof(*multi->table) << nb_bits);
+ if (!multi->table)
+ return AVERROR(ENOMEM);
+
+ j = code = 0;
+ for (int i = 0; i < nb_codes; i++, lens += lens_wrap) {
+ int len = *lens;
+ if (len > 0) {
+ unsigned sym;
+
+ buf[j].bits = len;
+ if (symbols)
+ GET_DATA(sym, symbols, i, symbols_wrap, symbols_size)
+ else
+ sym = i;
+ buf[j].symbol = sym + offset;
+ buf[j++].code = code;
+ } else if (len < 0) {
+ len = -len;
+ } else
+ continue;
+ if (len > len_max || code & ((1U << (32 - len)) - 1)) {
+ av_log(logctx, AV_LOG_ERROR, "Invalid VLC (length %u)\n", len);
+ goto fail;
+ }
+ code += 1U << (32 - len);
+ if (code > UINT32_MAX + 1ULL) {
+ av_log(logctx, AV_LOG_ERROR, "Overdetermined VLC tree\n");
+ goto fail;
+ }
+ }
+ ret = vlc_common_end(vlc, nb_bits, j, buf, flags, localbuf);
+ if (ret < 0)
+ goto fail;
+ return vlc_multi_gen(multi->table, vlc, nb_elems, j, nb_bits, buf, logctx);
+fail:
+ if (buf != localbuf)
+ av_free(buf);
+ return AVERROR_INVALIDDATA;
+}
+
+void ff_free_vlc_multi(VLC_MULTI *vlc)
+{
+ av_freep(&vlc->table);
+}
+
void ff_free_vlc(VLC *vlc)
{
av_freep(&vlc->table);
diff --git a/libavcodec/vlc.h b/libavcodec/vlc.h
index e63c484755..46063862f6 100644
--- a/libavcodec/vlc.h
+++ b/libavcodec/vlc.h
@@ -21,6 +21,8 @@
#include <stdint.h>
+#define VLC_MULTI_MAX_SYMBOLS 6
+
// When changing this, be sure to also update tableprint_vlc.h accordingly.
typedef int16_t VLCBaseType;
@@ -34,6 +36,17 @@ typedef struct VLC {
int table_size, table_allocated;
} VLC;
+typedef struct VLC_MULTI_ELEM {
+ uint8_t val[VLC_MULTI_MAX_SYMBOLS];
+ int8_t len; // -31,32
+ uint8_t num;
+} VLC_MULTI_ELEM;
+
+typedef struct VLC_MULTI {
+ VLC_MULTI_ELEM *table;
+ int table_size, table_allocated;
+} VLC_MULTI;
+
typedef struct RL_VLC_ELEM {
int16_t level;
int8_t len;
@@ -89,6 +102,46 @@ int ff_init_vlc_from_lengths(VLC *vlc, int nb_bits, int nb_codes,
const void *symbols, int symbols_wrap, int symbols_size,
int offset, int flags, void *logctx);
+/**
+ * Build VLC decoding tables suitable for use with get_vlc_multi()
+ *
+ * This function takes lengths and symbols and calculates the codes from them.
+ * For this the input lengths and symbols have to be sorted according to "left
+ * nodes in the corresponding tree first".
+ *
+ * @param[in,out] vlc The VLC to be initialized; table and table_allocated
+ * must have been set when initializing a static VLC,
+ * otherwise this will be treated as uninitialized.
+ * @param[in,out] multi The VLC_MULTI to be initialized; table and table_allocated
+ * must have been set when initializing a static VLC,
+ * otherwise this will be treated as uninitialized.
+ * @param[in] nb_bits The number of bits to use for the VLC table;
+ * higher values take up more memory and cache, but
+ * allow to read codes with fewer reads.
+ * @param[in] nb_elems The max possible number of elements.
+ * @param[in] nb_codes The number of provided length and (if supplied) symbol
+ * entries.
+ * @param[in] lens The lengths of the codes. Entries > 0 correspond to
+ * valid codes; entries == 0 will be skipped and entries
+ * with len < 0 indicate that the tree is incomplete and
+ * has an open end of length -len at this position.
+ * @param[in] lens_wrap Stride (in bytes) of the lengths.
+ * @param[in] symbols The symbols, i.e. what is returned from get_vlc2()
+ * when the corresponding code is encountered.
+ * May be NULL, then 0, 1, 2, 3, 4,... will be used.
+ * @param[in] symbols_wrap Stride (in bytes) of the symbols.
+ * @param[in] symbols_size Size of the symbols. 1 and 2 are supported.
+ * @param[in] offset An offset to apply to all the valid symbols.
+ * @param[in] flags A combination of the INIT_VLC_* flags; notice that
+ * INIT_VLC_INPUT_LE is pointless and ignored.
+ */
+int ff_init_vlc_multi_from_lengths(VLC *vlc, VLC_MULTI *multi, int nb_bits, int nb_elems,
+ int nb_codes, const int8_t *lens, int lens_wrap,
+ const void *symbols, int symbols_wrap, int symbols_size,
+ int offset, int flags, void *logctx);
+
+
+void ff_free_vlc_multi(VLC_MULTI *vlc);
void ff_free_vlc(VLC *vlc);
/* If INIT_VLC_INPUT_LE is set, the LSB bit of the codes used to
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