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alac: add option to decoded incorrect ALAC

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Prior to 56.1.100, incorrect ALAC files for 24bps content were produced, in
particular not decoding losslessly.

Add an option to allow correctly decoding those streams.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Christophe Gisquet 2014-08-18 09:53:20 +02:00 committed by Michael Niedermayer
parent cdd0ad7be1
commit 30cac8313a
1 changed files with 24 additions and 1 deletions
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25
libavcodec/alac.c
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@ -48,6 +48,7 @@
#include <inttypes.h>
#include "libavutil/channel_layout.h"
#include "libavutil/opt.h"
#include "avcodec.h"
#include "get_bits.h"
#include "bytestream.h"
@ -60,6 +61,7 @@
#define ALAC_EXTRADATA_SIZE 36
typedef struct {
AVClass *class;
AVCodecContext *avctx;
GetBitContext gb;
int channels;
@ -78,6 +80,7 @@ typedef struct {
int nb_samples; /**< number of samples in the current frame */
int direct_output;
int extra_bit_bug;
} ALACContext;
static inline unsigned int decode_scalar(GetBitContext *gb, int k, int bps)
@ -380,12 +383,17 @@ static int decode_element(AVCodecContext *avctx, AVFrame *frame, int ch_index,
decorr_left_weight = 0;
}
if (alac->extra_bits && alac->extra_bit_bug) {
append_extra_bits(alac->output_samples_buffer, alac->extra_bits_buffer,
alac->extra_bits, channels, alac->nb_samples);
}
if (channels == 2 && decorr_left_weight) {
decorrelate_stereo(alac->output_samples_buffer, alac->nb_samples,
decorr_shift, decorr_left_weight);
}
if (alac->extra_bits) {
if (alac->extra_bits && !alac->extra_bit_bug) {
append_extra_bits(alac->output_samples_buffer, alac->extra_bits_buffer,
alac->extra_bits, channels, alac->nb_samples);
}
@ -630,6 +638,20 @@ static int init_thread_copy(AVCodecContext *avctx)
return allocate_buffers(alac);
}
static const AVOption options[] = {
{ "extra_bits_bug", "Force non-standard decoding process",
offsetof(ALACContext, extra_bit_bug), AV_OPT_TYPE_INT, { .i64 = 0 },
0, 1, AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_DECODING_PARAM },
{ NULL },
};
static const AVClass alac_class = {
.class_name = "alac",
.item_name = av_default_item_name,
.option = options,
.version = LIBAVUTIL_VERSION_INT,
};
AVCodec ff_alac_decoder = {
.name = "alac",
.long_name = NULL_IF_CONFIG_SMALL("ALAC (Apple Lossless Audio Codec)"),
@ -641,4 +663,5 @@ AVCodec ff_alac_decoder = {
.decode = alac_decode_frame,
.init_thread_copy = ONLY_IF_THREADS_ENABLED(init_thread_copy),
.capabilities = CODEC_CAP_DR1 | CODEC_CAP_FRAME_THREADS,
.priv_class = &alac_class
};