From 646800f79ca478309fcf741e840ba5b5e795e533 Mon Sep 17 00:00:00 2001
From: Justin Ruggles <justin.ruggles@gmail.com>
Date: Sat, 5 Jan 2008 18:39:55 +0000
Subject: [PATCH] move E-AC3 header parsing to ff_ac3_parse_header()

Originally committed as revision 11420 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 libavcodec/ac3_parser.c | 84 ++++++++++++++++++-----------------------
 libavcodec/ac3dec.c     |  3 ++
 2 files changed, 40 insertions(+), 47 deletions(-)

diff --git a/libavcodec/ac3_parser.c b/libavcodec/ac3_parser.c
index 1b396bf6ac..604dac186a 100644
--- a/libavcodec/ac3_parser.c
+++ b/libavcodec/ac3_parser.c
@@ -38,6 +38,7 @@ int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr)
 {
     GetBitContext gbc;
     int frame_size_code;
+    int num_blocks;
 
     memset(hdr, 0, sizeof(*hdr));
 
@@ -47,11 +48,13 @@ int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr)
     if(hdr->sync_word != 0x0B77)
         return AC3_PARSE_ERROR_SYNC;
 
-    /* read ahead to bsid to make sure this is AC-3, not E-AC-3 */
+    /* read ahead to bsid to distinguish between AC-3 and E-AC-3 */
     hdr->bitstream_id = show_bits_long(&gbc, 29) & 0x1F;
-    if(hdr->bitstream_id > 10)
+    if(hdr->bitstream_id > 16)
         return AC3_PARSE_ERROR_BSID;
 
+    if(hdr->bitstream_id <= 10) {
+    /* Normal AC-3 */
     hdr->crc1 = get_bits(&gbc, 16);
     hdr->sr_code = get_bits(&gbc, 2);
     if(hdr->sr_code == 3)
@@ -81,6 +84,37 @@ int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr)
     hdr->bit_rate = (ff_ac3_bitrate_tab[frame_size_code>>1] * 1000) >> hdr->sr_shift;
     hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
     hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2;
+    } else {
+        /* Enhanced AC-3 */
+        hdr->crc1 = 0;
+        skip_bits(&gbc, 2); // skip stream type
+        skip_bits(&gbc, 3); // skip substream id
+
+        hdr->frame_size = (get_bits(&gbc, 11) + 1) << 1;
+        if(hdr->frame_size < AC3_HEADER_SIZE)
+            return AC3_PARSE_ERROR_FRAME_SIZE;
+
+        hdr->sr_code = get_bits(&gbc, 2);
+        if (hdr->sr_code == 3) {
+            int sr_code2 = get_bits(&gbc, 2);
+            if(sr_code2 == 3)
+                return AC3_PARSE_ERROR_SAMPLE_RATE;
+            hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
+            hdr->sr_shift = 1;
+            num_blocks = 6;
+        } else {
+            num_blocks = eac3_blocks[get_bits(&gbc, 2)];
+            hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code];
+            hdr->sr_shift = 0;
+        }
+
+        hdr->channel_mode = get_bits(&gbc, 3);
+        hdr->lfe_on = get_bits1(&gbc);
+
+        hdr->bit_rate = (uint32_t)(8.0 * hdr->frame_size * hdr->sample_rate /
+                        (num_blocks * 256.0));
+        hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
+    }
 
     return 0;
 }
@@ -89,62 +123,18 @@ static int ac3_sync(const uint8_t *buf, int *channels, int *sample_rate,
                     int *bit_rate, int *samples)
 {
     int err;
-    unsigned int sr_code, channel_mode, bitstream_id, lfe_on;
-    unsigned int stream_type, substream_id, frame_size, sr_code2, num_blocks_code;
-    GetBitContext bits;
     AC3HeaderInfo hdr;
 
     err = ff_ac3_parse_header(buf, &hdr);
 
-    if(err < 0 && err != -2)
+    if(err < 0)
         return 0;
 
-    bitstream_id = hdr.bitstream_id;
-    if(bitstream_id <= 10) {             /* Normal AC-3 */
         *sample_rate = hdr.sample_rate;
         *bit_rate = hdr.bit_rate;
         *channels = hdr.channels;
         *samples = AC3_FRAME_SIZE;
         return hdr.frame_size;
-    } else if (bitstream_id > 10 && bitstream_id <= 16) { /* Enhanced AC-3 */
-        init_get_bits(&bits, &buf[2], (AC3_HEADER_SIZE-2) * 8);
-        stream_type = get_bits(&bits, 2);
-        substream_id = get_bits(&bits, 3);
-
-        if (stream_type != 0 || substream_id != 0)
-            return 0;   /* Currently don't support additional streams */
-
-        frame_size = get_bits(&bits, 11) + 1;
-        if(frame_size*2 < AC3_HEADER_SIZE)
-            return 0;
-
-        sr_code = get_bits(&bits, 2);
-        if (sr_code == 3) {
-            sr_code2 = get_bits(&bits, 2);
-            num_blocks_code = 3;
-
-            if(sr_code2 == 3)
-                return 0;
-
-            *sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
-        } else {
-            num_blocks_code = get_bits(&bits, 2);
-
-            *sample_rate = ff_ac3_sample_rate_tab[sr_code];
-        }
-
-        channel_mode = get_bits(&bits, 3);
-        lfe_on = get_bits1(&bits);
-
-        *samples = eac3_blocks[num_blocks_code] * 256;
-        *bit_rate = frame_size * (*sample_rate) * 16 / (*samples);
-        *channels = ff_ac3_channels_tab[channel_mode] + lfe_on;
-
-        return frame_size * 2;
-    }
-
-    /* Unsupported bitstream version */
-    return 0;
 }
 
 static int ac3_parse_init(AVCodecParserContext *s1)
diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
index 660d8f64d5..76cf1add0e 100644
--- a/libavcodec/ac3dec.c
+++ b/libavcodec/ac3dec.c
@@ -338,6 +338,9 @@ static int ac3_parse_header(AC3DecodeContext *s)
     if(err)
         return err;
 
+    if(hdr.bitstream_id > 10)
+        return AC3_PARSE_ERROR_BSID;
+
     /* get decoding parameters from header info */
     s->bit_alloc_params.sr_code     = hdr.sr_code;
     s->channel_mode                 = hdr.channel_mode;