Hi,
this is a proposal to allow decoding incorrect files. There is no
obvious and systematic way to detect them however.
--
Christophe
From feaacb09d8660b7e8784ad4a550dda455f172e24 Mon Sep 17 00:00:00 2001
From: Christophe Gisquet <christophe.gisq...@gmail.com>
Date: Mon, 18 Aug 2014 09:53:20 +0200
Subject: [PATCH] alac: add option to decoded incorrect ALAC
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.
---
libavcodec/alac.c | 24 +++++++++++++++++++++++-
libavcodec/version.h | 4 ++--
2 files changed, 25 insertions(+), 3 deletions(-)
diff --git a/libavcodec/alac.c b/libavcodec/alac.c
index 103d14e..849d623 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"
@@ -78,6 +79,7 @@ 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 +382,17 @@ 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 +637,20 @@ 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 +662,5 @@ 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
};
diff --git a/libavcodec/version.h b/libavcodec/version.h
index 2c871ba..19e2e45 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -29,8 +29,8 @@
#include "libavutil/version.h"
#define LIBAVCODEC_VERSION_MAJOR 56
-#define LIBAVCODEC_VERSION_MINOR 0
-#define LIBAVCODEC_VERSION_MICRO 101
+#define LIBAVCODEC_VERSION_MINOR 1
+#define LIBAVCODEC_VERSION_MICRO 100
#define LIBAVCODEC_VERSION_INT AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
LIBAVCODEC_VERSION_MINOR, \
--
1.9.2.msysgit.0
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