diff options
author | Justin Ruggles <justin.ruggles@gmail.com> | 2011-12-07 20:55:24 +0400 |
---|---|---|
committer | Justin Ruggles <justin.ruggles@gmail.com> | 2012-01-03 22:15:23 +0400 |
commit | e76c7b856f7aab9d8e3a42f61142eda30fc0749e (patch) | |
tree | 8091ba4969dc2d6020631e752b7280eaf0983583 /libavcodec/alac.c | |
parent | 490dcda6b6051066ad7d83979d81db5506f9b3eb (diff) |
alacdec: fill in missing or guessed info about the extradata format.
Now that there is official documentation from Apple about this, we don't have
to guess anymore.
Diffstat (limited to 'libavcodec/alac.c')
-rw-r--r-- | libavcodec/alac.c | 38 |
1 files changed, 17 insertions, 21 deletions
diff --git a/libavcodec/alac.c b/libavcodec/alac.c index 47234ecf13..eb6c1cfc16 100644 --- a/libavcodec/alac.c +++ b/libavcodec/alac.c @@ -25,27 +25,23 @@ * @author 2005 David Hammerton * @see http://crazney.net/programs/itunes/alac.html * - * Note: This decoder expects a 36- (0x24-)byte QuickTime atom to be + * Note: This decoder expects a 36-byte QuickTime atom to be * passed through the extradata[_size] fields. This atom is tacked onto * the end of an 'alac' stsd atom and has the following format: - * bytes 0-3 atom size (0x24), big-endian - * bytes 4-7 atom type ('alac', not the 'alac' tag from start of stsd) - * bytes 8-35 data bytes needed by decoder * - * Extradata: - * 32bit size - * 32bit tag (=alac) - * 32bit zero? - * 32bit max sample per frame - * 8bit ?? (zero?) + * 32bit atom size + * 32bit tag ("alac") + * 32bit tag version (0) + * 32bit samples per frame (used when not set explicitly in the frames) + * 8bit compatible version (0) * 8bit sample size - * 8bit history mult - * 8bit initial history - * 8bit kmodifier - * 8bit channels? - * 16bit ?? - * 32bit max coded frame size - * 32bit bitrate? + * 8bit history mult (40) + * 8bit initial history (14) + * 8bit kmodifier (10) + * 8bit channels + * 16bit maxRun (255) + * 32bit max coded frame size (0 means unknown) + * 32bit average bitrate (0 means unknown) * 32bit samplerate */ @@ -574,7 +570,7 @@ static int alac_set_info(ALACContext *alac) ptr += 4; /* size */ ptr += 4; /* alac */ - ptr += 4; /* 0 ? */ + ptr += 4; /* version */ if(AV_RB32(ptr) >= UINT_MAX/4){ av_log(alac->avctx, AV_LOG_ERROR, "setinfo_max_samples_per_frame too large\n"); @@ -583,15 +579,15 @@ static int alac_set_info(ALACContext *alac) /* buffer size / 2 ? */ alac->setinfo_max_samples_per_frame = bytestream_get_be32(&ptr); - ptr++; /* ??? */ + ptr++; /* compatible version */ alac->setinfo_sample_size = *ptr++; alac->setinfo_rice_historymult = *ptr++; alac->setinfo_rice_initialhistory = *ptr++; alac->setinfo_rice_kmodifier = *ptr++; alac->numchannels = *ptr++; - bytestream_get_be16(&ptr); /* ??? */ + bytestream_get_be16(&ptr); /* maxRun */ bytestream_get_be32(&ptr); /* max coded frame size */ - bytestream_get_be32(&ptr); /* bitrate ? */ + bytestream_get_be32(&ptr); /* average bitrate */ bytestream_get_be32(&ptr); /* samplerate */ return 0; |