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avcodec/mlpenc: Simplify finding best codebook 

Finding the best codebook involves comparing different paths, where each
path is a sequence of several decisions (namely which codebook to use).
Up until now, these sequence was encoded in a NUL-terminated string and
the actual decisions were encoded as ’\0'..'\3' (which encoded 0..3).
This commit modifies this to actually encode it via 0..3 by switching
away from a C-string to a simple array with an explicit length field.

Reviewed-by: Lynne <dev@lynne.ee>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2020-12-26 18:16:21 +01:00
parent 2825ed4e26
commit 15072d2753
1 changed files with 10 additions and 24 deletions
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34
libavcodec/mlpenc.c
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@ -1947,24 +1947,16 @@ static void rematrix_channels(MLPEncodeContext *ctx)
****************************************************************************/
typedef struct {
char path[MAJOR_HEADER_INTERVAL + 3];
char path[MAJOR_HEADER_INTERVAL + 2];
int cur_idx;
int bitcount;
} PathCounter;
static const char *path_counter_codebook[] = { "0", "1", "2", "3", };
#define ZERO_PATH '0'
#define CODEBOOK_CHANGE_BITS 21
static void clear_path_counter(PathCounter *path_counter)
{
unsigned int i;
for (i = 0; i < NUM_CODEBOOKS + 1; i++) {
path_counter[i].path[0] = ZERO_PATH;
path_counter[i].path[1] = 0x00;
path_counter[i].bitcount = 0;
}
memset(path_counter, 0, (NUM_CODEBOOKS + 1) * sizeof(*path_counter));
}
static int compare_best_offset(BestOffset *prev, BestOffset *cur)
@ -1978,18 +1970,11 @@ static int compare_best_offset(BestOffset *prev, BestOffset *cur)
static int best_codebook_path_cost(MLPEncodeContext *ctx, unsigned int channel,
PathCounter *src, int cur_codebook)
{
BestOffset *cur_bo, *prev_bo = restart_best_offset;
int idx = src->cur_idx;
BestOffset *cur_bo = ctx->best_offset[idx][channel],
*prev_bo = idx ? ctx->best_offset[idx - 1][channel] : restart_best_offset;
int bitcount = src->bitcount;
char *path = src->path + 1;
int prev_codebook;
int i;
for (i = 0; path[i]; i++)
prev_bo = ctx->best_offset[i][channel];
prev_codebook = path[i - 1] - ZERO_PATH;
cur_bo = ctx->best_offset[i][channel];
int prev_codebook = src->path[idx];
bitcount += cur_bo[cur_codebook].bitcount;
@ -2052,7 +2037,8 @@ static void set_best_codebook(MLPEncodeContext *ctx)
prev_best_bitcount = temp_bitcount;
if (src_path != dst_path)
memcpy(dst_path, src_path, sizeof(PathCounter));
av_strlcat(dst_path->path, path_counter_codebook[codebook], sizeof(dst_path->path));
if (dst_path->cur_idx < FF_ARRAY_ELEMS(dst_path->path) - 1)
dst_path->path[++dst_path->cur_idx] = codebook;
dst_path->bitcount = temp_bitcount;
}
}
@ -2069,7 +2055,7 @@ static void set_best_codebook(MLPEncodeContext *ctx)
for (index = 0; index < ctx->number_of_subblocks; index++) {
ChannelParams *cp = ctx->seq_channel_params + index*(ctx->avctx->channels) + channel;
best_codebook = *best_path++ - ZERO_PATH;
best_codebook = *best_path++;
cur_bo = &ctx->best_offset[index][channel][best_codebook];
cp->huff_offset = cur_bo->offset;