Move decode_frame_header() from flacdec.c to flac.c/h to share with the

forthcoming FLAC parser.
Patch by Michael Chinen [mchinen at gmail]

Originally committed as revision 25909 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 94 insertions, 0 deletions

diff --git a/libavcodec/flac.c b/libavcodec/flac.c
index a649e08732..f6b65ce5e9 100644
--- a/libavcodec/flac.c
+++ b/libavcodec/flac.c
@@ -19,7 +19,101 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include "libavutil/crc.h"
 #include "flac.h"
+#include "flacdata.h"
+
+static const int8_t sample_size_table[] = { 0, 8, 12, 0, 16, 20, 24, 0 };
+
+static int64_t get_utf8(GetBitContext *gb)
+{
+    int64_t val;
+    GET_UTF8(val, get_bits(gb, 8), return -1;)
+    return val;
+}
+
+int ff_flac_decode_frame_header(AVCodecContext *avctx, GetBitContext *gb,
+                                FLACFrameInfo *fi)
+{
+    int bs_code, sr_code, bps_code;
+
+    /* frame sync code */
+    skip_bits(gb, 16);
+
+    /* block size and sample rate codes */
+    bs_code = get_bits(gb, 4);
+    sr_code = get_bits(gb, 4);
+
+    /* channels and decorrelation */
+    fi->ch_mode = get_bits(gb, 4);
+    if (fi->ch_mode < FLAC_MAX_CHANNELS) {
+        fi->channels = fi->ch_mode + 1;
+        fi->ch_mode = FLAC_CHMODE_INDEPENDENT;
+    } else if (fi->ch_mode <= FLAC_CHMODE_MID_SIDE) {
+        fi->channels = 2;
+    } else {
+        av_log(avctx, AV_LOG_ERROR, "invalid channel mode: %d\n", fi->ch_mode);
+        return -1;
+    }
+
+    /* bits per sample */
+    bps_code = get_bits(gb, 3);
+    if (bps_code == 3 || bps_code == 7) {
+        av_log(avctx, AV_LOG_ERROR, "invalid sample size code (%d)\n",
+               bps_code);
+        return -1;
+    }
+    fi->bps = sample_size_table[bps_code];
+
+    /* reserved bit */
+    if (get_bits1(gb)) {
+        av_log(avctx, AV_LOG_ERROR, "broken stream, invalid padding\n");
+        return -1;
+    }
+
+    /* sample or frame count */
+    if (get_utf8(gb) < 0) {
+        av_log(avctx, AV_LOG_ERROR, "utf8 fscked\n");
+        return -1;
+    }
+
+    /* blocksize */
+    if (bs_code == 0) {
+        av_log(avctx, AV_LOG_ERROR, "reserved blocksize code: 0\n");
+        return -1;
+    } else if (bs_code == 6) {
+        fi->blocksize = get_bits(gb, 8) + 1;
+    } else if (bs_code == 7) {
+        fi->blocksize = get_bits(gb, 16) + 1;
+    } else {
+        fi->blocksize = ff_flac_blocksize_table[bs_code];
+    }
+
+    /* sample rate */
+    if (sr_code < 12) {
+        fi->samplerate = ff_flac_sample_rate_table[sr_code];
+    } else if (sr_code == 12) {
+        fi->samplerate = get_bits(gb, 8) * 1000;
+    } else if (sr_code == 13) {
+        fi->samplerate = get_bits(gb, 16);
+    } else if (sr_code == 14) {
+        fi->samplerate = get_bits(gb, 16) * 10;
+    } else {
+        av_log(avctx, AV_LOG_ERROR, "illegal sample rate code %d\n",
+               sr_code);
+        return -1;
+    }
+
+    /* header CRC-8 check */
+    skip_bits(gb, 8);
+    if (av_crc(av_crc_get_table(AV_CRC_8_ATM), 0, gb->buffer,
+               get_bits_count(gb)/8)) {
+        av_log(avctx, AV_LOG_ERROR, "header crc mismatch\n");
+        return -1;
+    }
+
+    return 0;
+}
 
 int ff_flac_get_max_frame_size(int blocksize, int ch, int bps)
 {