From e027d0a81ee012b3876a616f49dd84be66ff34f5 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michaelni@gmx.at>
Date: Mon, 6 Mar 2006 14:53:13 +0000
Subject: [PATCH] switch ac3enc to av_crc

Originally committed as revision 5116 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 libavcodec/ac3enc.c | 35 +++--------------------------------
 libavcodec/ac3tab.h |  2 --
 libavcodec/utils.c  |  2 ++
 3 files changed, 5 insertions(+), 34 deletions(-)

diff --git a/libavcodec/ac3enc.c b/libavcodec/ac3enc.c
index 0f9badf5ec..508439480a 100644
--- a/libavcodec/ac3enc.c
+++ b/libavcodec/ac3enc.c
@@ -25,6 +25,7 @@
 //#define DEBUG_BITALLOC
 #include "avcodec.h"
 #include "bitstream.h"
+#include "crc.h"
 #include "ac3.h"
 
 typedef struct AC3EncodeContext {
@@ -66,7 +67,6 @@ typedef struct AC3EncodeContext {
 #define EXP_DIFF_THRESHOLD 1000
 
 static void fft_init(int ln);
-static void ac3_crc_init(void);
 
 static inline int16_t fix15(float a)
 {
@@ -886,8 +886,6 @@ static int AC3_encode_init(AVCodecContext *avctx)
         xsin1[i] = fix15(-sin(alpha));
     }
 
-    ac3_crc_init();
-
     avctx->coded_frame= avcodec_alloc_frame();
     avctx->coded_frame->key_frame= 1;
 
@@ -1236,35 +1234,8 @@ static void output_audio_block(AC3EncodeContext *s,
     }
 }
 
-/* compute the ac3 crc */
-
 #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
 
-static void ac3_crc_init(void)
-{
-    unsigned int c, n, k;
-
-    for(n=0;n<256;n++) {
-        c = n << 8;
-        for (k = 0; k < 8; k++) {
-            if (c & (1 << 15))
-                c = ((c << 1) & 0xffff) ^ (CRC16_POLY & 0xffff);
-            else
-                c = c << 1;
-        }
-        crc_table[n] = c;
-    }
-}
-
-static unsigned int ac3_crc(uint8_t *data, int n, unsigned int crc)
-{
-    int i;
-    for(i=0;i<n;i++) {
-        crc = (crc_table[data[i] ^ (crc >> 8)] ^ (crc << 8)) & 0xffff;
-    }
-    return crc;
-}
-
 static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
 {
     unsigned int c;
@@ -1342,14 +1313,14 @@ static int output_frame_end(AC3EncodeContext *s)
     /* Now we must compute both crcs : this is not so easy for crc1
        because it is at the beginning of the data... */
     frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
-    crc1 = ac3_crc(frame + 4, (2 * frame_size_58) - 4, 0);
+    crc1 = bswap_16(av_crc(av_crc8005, 0, frame + 4, 2 * frame_size_58 - 4));
     /* XXX: could precompute crc_inv */
     crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
     crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
     frame[2] = crc1 >> 8;
     frame[3] = crc1;
 
-    crc2 = ac3_crc(frame + 2 * frame_size_58, (frame_size - frame_size_58) * 2 - 2, 0);
+    crc2 = bswap_16(av_crc(av_crc8005, 0, frame + 2 * frame_size_58, (frame_size - frame_size_58) * 2 - 2));
     frame[2*frame_size - 2] = crc2 >> 8;
     frame[2*frame_size - 1] = crc2;
 
diff --git a/libavcodec/ac3tab.h b/libavcodec/ac3tab.h
index c56bf58dea..d8771fbeee 100644
--- a/libavcodec/ac3tab.h
+++ b/libavcodec/ac3tab.h
@@ -182,5 +182,3 @@ static int16_t sintab[64];
 static int16_t fft_rev[512];
 static int16_t xcos1[128];
 static int16_t xsin1[128];
-
-static uint16_t crc_table[256];
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 5e98a54ced..e73590b320 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -1221,7 +1221,9 @@ unsigned avcodec_build( void )
 
 static void init_crcs(void){
     av_crc04C11DB7= av_mallocz_static(sizeof(AVCRC) * 257);
+    av_crc8005    = av_mallocz_static(sizeof(AVCRC) * 257);
     av_crc_init(av_crc04C11DB7, 0, 32, 0x04c11db7, sizeof(AVCRC)*257);
+    av_crc_init(av_crc8005    , 0, 16, 0x8005    , sizeof(AVCRC)*257);
 }
 
 /* must be called before any other functions */