From c7516a000c4c6469543326779da87995d8d15dd3 Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Tue, 9 Mar 2004 15:23:14 +0000 Subject: [PATCH] find_start_code() optimization (about 2x faster now) this may improve decoding speed with multiple threads Originally committed as revision 2862 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavcodec/mpeg12.c | 31 +++++++++++++++++-------------- 1 file changed, 17 insertions(+), 14 deletions(-) diff --git a/libavcodec/mpeg12.c b/libavcodec/mpeg12.c index 1bf66e7896..28a6791f30 100644 --- a/libavcodec/mpeg12.c +++ b/libavcodec/mpeg12.c @@ -1770,24 +1770,27 @@ static int mpeg_decode_init(AVCodecContext *avctx) state. Return -1 if no start code found */ static int find_start_code(const uint8_t **pbuf_ptr, const uint8_t *buf_end) { - const uint8_t *buf_ptr; - unsigned int state=0xFFFFFFFF, v; - int val; + const uint8_t *buf_ptr= *pbuf_ptr; + + buf_ptr++; //gurantees that -1 is within the array + buf_end -= 2; // gurantees that +2 is within the array - buf_ptr = *pbuf_ptr; while (buf_ptr < buf_end) { - v = *buf_ptr++; - if (state == 0x000001) { - state = ((state << 8) | v) & 0xffffff; - val = state; - goto found; + if(*buf_ptr==0){ + while(buf_ptr < buf_end && buf_ptr[1]==0) + buf_ptr++; + + if(buf_ptr[-1] == 0 && buf_ptr[1] == 1){ + *pbuf_ptr = buf_ptr+3; + return buf_ptr[2] + 0x100; + } } - state = ((state << 8) | v) & 0xffffff; + buf_ptr += 2; } - val = -1; - found: - *pbuf_ptr = buf_ptr; - return val; + buf_end += 2; //undo the hack above + + *pbuf_ptr = buf_end; + return -1; } static int mpeg1_decode_picture(AVCodecContext *avctx,