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Parse and drop gain control data, so that SSR packets decode.

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This will result in poor quality audio for SSR streams, but they
will at least demux and decode without error; partially fixing
ticket #1693.

This pulls in the decode_gain_control() function from the
ffmpeg summer-of-code repo (original author Maxim Gavrilov) at
svn://svn.mplayerhq.hu/soc/aac/aac.c with some minor modifications
and adds AOT_AAC_SSR to decode_audio_specific_config_gb().

Signed-off-by: Dale Curtis <dalecurtis@chromium.org>
Co-authored-by: Maxim Gavrilov <maxim.gavrilov@gmail.com>
This commit is contained in:
Dale Curtis 2018-02-15 16:22:55 -08:00 committed by Alex Converse
parent cd98f20b4a
commit a246701e9a
2 changed files with 35 additions and 3 deletions
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2
libavcodec/aac.h
View File

@ -357,6 +357,8 @@ struct AACContext {
int warned_num_aac_frames;
int warned_960_sbr;
int warned_gain_control;
/* aacdec functions pointers */
void (*imdct_and_windowing)(AACContext *ac, SingleChannelElement *sce);
void (*apply_ltp)(AACContext *ac, SingleChannelElement *sce);

36
libavcodec/aacdec_template.c
View File

@ -997,6 +997,7 @@ static int decode_audio_specific_config_gb(AACContext *ac,
switch (m4ac->object_type) {
case AOT_AAC_MAIN:
case AOT_AAC_LC:
case AOT_AAC_SSR:
case AOT_AAC_LTP:
case AOT_ER_AAC_LC:
case AOT_ER_AAC_LD:
@ -1967,6 +1968,33 @@ static void apply_prediction(AACContext *ac, SingleChannelElement *sce)
reset_all_predictors(sce->predictor_state);
}
static void decode_gain_control(SingleChannelElement * sce, GetBitContext * gb)
{
// wd_num, wd_test, aloc_size
static const uint8_t gain_mode[4][3] = {
{1, 0, 5}, // ONLY_LONG_SEQUENCE = 0,
{2, 1, 2}, // LONG_START_SEQUENCE,
{8, 0, 2}, // EIGHT_SHORT_SEQUENCE,
{2, 1, 5}, // LONG_STOP_SEQUENCE
};
const int mode = sce->ics.window_sequence[0];
uint8_t bd, wd, ad;
// FIXME: Store the gain control data on |sce| and do something with it.
uint8_t max_band = get_bits(gb, 2);
for (bd = 0; bd < max_band; bd++) {
for (wd = 0; wd < gain_mode[mode][0]; wd++) {
uint8_t adjust_num = get_bits(gb, 3);
for (ad = 0; ad < adjust_num; ad++) {
skip_bits(gb, 4 + ((wd == 0 && gain_mode[mode][1])
? 4
: gain_mode[mode][2]));
}
}
}
}
/**
* Decode an individual_channel_stream payload; reference: table 4.44.
*
@ -2034,9 +2062,11 @@ static int decode_ics(AACContext *ac, SingleChannelElement *sce,
goto fail;
}
if (!eld_syntax && get_bits1(gb)) {
avpriv_request_sample(ac->avctx, "SSR");
ret = AVERROR_PATCHWELCOME;
goto fail;
decode_gain_control(sce, gb);
if (!ac->warned_gain_control) {
avpriv_report_missing_feature(ac->avctx, "Gain control");
ac->warned_gain_control = 1;
}
}
// I see no textual basis in the spec for this occurring after SSR gain
// control, but this is what both reference and real implmentations do