Prior to 56.1.100, incorrect ALAC files for 24bps content were produced, in
particular not decoding losslessly.
Add the codec option extra_bits_bug to allow correctly decoding those
streams.
---
libavcodec/alac.c | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)
diff --git a/libavcodec/alac.c b/libavcodec/alac.c
index 5272f84..0776b4f 100644
--- a/libavcodec/alac.c
+++ b/libavcodec/alac.c
@@ -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"
@@ -59,6 +60,7 @@
#define ALAC_EXTRADATA_SIZE 36
typedef struct {
+ AVClass *class;
AVCodecContext *avctx;
GetBitContext gb;
int channels;
@@ -75,6 +77,8 @@ typedef struct {
int extra_bits; /**< number of extra bits beyond 16-bit */
int nb_samples; /**< number of samples in the current frame */
+
+ int extra_bit_bug;
} ALACContext;
static inline unsigned int decode_scalar(GetBitContext *gb, int k, int bps)
@@ -368,12 +372,17 @@ 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);
}
@@ -572,6 +581,20 @@ static av_cold int alac_decode_init(AVCodecContext * avctx)
return 0;
}
+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)"),
@@ -582,4 +605,5 @@ AVCodec ff_alac_decoder = {
.close = alac_decode_close,
.decode = alac_decode_frame,
.capabilities = CODEC_CAP_DR1,
+ .priv_class = &alac_class
};
--
1.9.2.msysgit.0
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