[FFmpeg-cvslog] avcodec/alac: reduce dereferencing inside loops
Paul B Mahol
git at videolan.org
Tue Aug 15 20:11:44 EEST 2023
ffmpeg | branch: master | Paul B Mahol <onemda at gmail.com> | Tue Aug 15 18:43:26 2023 +0200| [4463778aab8f01c9acf02b23d41a61df32ccfe88] | committer: Paul B Mahol
avcodec/alac: reduce dereferencing inside loops
Also fix style while here.
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=4463778aab8f01c9acf02b23d41a61df32ccfe88
---
libavcodec/alac.c | 52 ++++++++++++++++++++++++++++------------------------
1 file changed, 28 insertions(+), 24 deletions(-)
diff --git a/libavcodec/alac.c b/libavcodec/alac.c
index d10ecba7e6..13754d407d 100644
--- a/libavcodec/alac.c
+++ b/libavcodec/alac.c
@@ -112,6 +112,7 @@ static inline unsigned int decode_scalar(GetBitContext *gb, int k, int bps)
static int rice_decompress(ALACContext *alac, int32_t *output_buffer,
int nb_samples, int bps, int rice_history_mult)
{
+ GetBitContext *gb = &alac->gb;
int i;
unsigned int history = alac->rice_initial_history;
int sign_modifier = 0;
@@ -120,13 +121,13 @@ static int rice_decompress(ALACContext *alac, int32_t *output_buffer,
int k;
unsigned int x;
- if(get_bits_left(&alac->gb) <= 0)
+ if (get_bits_left(gb) <= 0)
return AVERROR_INVALIDDATA;
/* calculate rice param and decode next value */
k = av_log2((history >> 9) + 3);
k = FFMIN(k, alac->rice_limit);
- x = decode_scalar(&alac->gb, k, bps);
+ x = decode_scalar(gb, k, bps);
x += sign_modifier;
sign_modifier = 0;
output_buffer[i] = (x >> 1) ^ -(x & 1);
@@ -145,7 +146,7 @@ static int rice_decompress(ALACContext *alac, int32_t *output_buffer,
/* calculate rice param and decode block size */
k = 7 - av_log2(history) + ((history + 16) >> 6);
k = FFMIN(k, alac->rice_limit);
- block_size = decode_scalar(&alac->gb, k, 16);
+ block_size = decode_scalar(gb, k, 16);
if (block_size > 0) {
if (block_size >= nb_samples - i) {
@@ -239,16 +240,17 @@ static int decode_element(AVCodecContext *avctx, AVFrame *frame, int ch_index,
{
ALACContext *alac = avctx->priv_data;
int has_size, bps, is_compressed, decorr_shift, decorr_left_weight, ret;
+ GetBitContext *gb = &alac->gb;
uint32_t output_samples;
int i, ch;
- skip_bits(&alac->gb, 4); /* element instance tag */
- skip_bits(&alac->gb, 12); /* unused header bits */
+ skip_bits(gb, 4); /* element instance tag */
+ skip_bits(gb, 12); /* unused header bits */
/* the number of output samples is stored in the frame */
- has_size = get_bits1(&alac->gb);
+ has_size = get_bits1(gb);
- alac->extra_bits = get_bits(&alac->gb, 2) << 3;
+ alac->extra_bits = get_bits(gb, 2) << 3;
bps = alac->sample_size - alac->extra_bits + channels - 1;
if (bps > 32) {
avpriv_report_missing_feature(avctx, "bps %d", bps);
@@ -258,10 +260,10 @@ static int decode_element(AVCodecContext *avctx, AVFrame *frame, int ch_index,
return AVERROR_INVALIDDATA;
/* whether the frame is compressed */
- is_compressed = !get_bits1(&alac->gb);
+ is_compressed = !get_bits1(gb);
if (has_size)
- output_samples = get_bits_long(&alac->gb, 32);
+ output_samples = get_bits_long(gb, 32);
else
output_samples = alac->max_samples_per_frame;
if (!output_samples || output_samples > alac->max_samples_per_frame) {
@@ -298,39 +300,40 @@ static int decode_element(AVCodecContext *avctx, AVFrame *frame, int ch_index,
return AVERROR(ENOSYS);
}
- decorr_shift = get_bits(&alac->gb, 8);
- decorr_left_weight = get_bits(&alac->gb, 8);
+ decorr_shift = get_bits(gb, 8);
+ decorr_left_weight = get_bits(gb, 8);
if (channels == 2 && decorr_left_weight && decorr_shift > 31)
return AVERROR_INVALIDDATA;
for (ch = 0; ch < channels; ch++) {
- prediction_type[ch] = get_bits(&alac->gb, 4);
- lpc_quant[ch] = get_bits(&alac->gb, 4);
- rice_history_mult[ch] = get_bits(&alac->gb, 3);
- lpc_order[ch] = get_bits(&alac->gb, 5);
+ prediction_type[ch] = get_bits(gb, 4);
+ lpc_quant[ch] = get_bits(gb, 4);
+ rice_history_mult[ch] = get_bits(gb, 3);
+ lpc_order[ch] = get_bits(gb, 5);
if (lpc_order[ch] >= alac->max_samples_per_frame || !lpc_quant[ch])
return AVERROR_INVALIDDATA;
/* read the predictor table */
for (i = lpc_order[ch] - 1; i >= 0; i--)
- lpc_coefs[ch][i] = get_sbits(&alac->gb, 16);
+ lpc_coefs[ch][i] = get_sbits(gb, 16);
}
if (alac->extra_bits) {
+ const int extra_bits = alac->extra_bits;
+ if (get_bits_left(gb) < (int64_t)alac->nb_samples * channels * extra_bits)
+ return AVERROR_INVALIDDATA;
for (i = 0; i < alac->nb_samples; i++) {
- if(get_bits_left(&alac->gb) <= 0)
- return AVERROR_INVALIDDATA;
for (ch = 0; ch < channels; ch++)
- alac->extra_bits_buffer[ch][i] = get_bits(&alac->gb, alac->extra_bits);
+ alac->extra_bits_buffer[ch][i] = get_bits(gb, extra_bits);
}
}
for (ch = 0; ch < channels; ch++) {
- int ret=rice_decompress(alac, alac->predict_error_buffer[ch],
+ int ret = rice_decompress(alac, alac->predict_error_buffer[ch],
alac->nb_samples, bps,
rice_history_mult[ch] * alac->rice_history_mult / 4);
- if(ret<0)
+ if (ret < 0)
return ret;
/* adaptive FIR filter */
@@ -354,13 +357,14 @@ static int decode_element(AVCodecContext *avctx, AVFrame *frame, int ch_index,
bps, lpc_coefs[ch], lpc_order[ch], lpc_quant[ch]);
}
} else {
+ const int sample_size = alac->sample_size;
/* not compressed, easy case */
+ if (get_bits_left(gb) < (int64_t)alac->nb_samples * channels * sample_size)
+ return AVERROR_INVALIDDATA;
for (i = 0; i < alac->nb_samples; i++) {
- if(get_bits_left(&alac->gb) <= 0)
- return AVERROR_INVALIDDATA;
for (ch = 0; ch < channels; ch++) {
alac->output_samples_buffer[ch][i] =
- get_sbits_long(&alac->gb, alac->sample_size);
+ get_sbits_long(gb, sample_size);
}
}
alac->extra_bits = 0;
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