[FFmpeg-devel] [PATCH 3/8] avpriv_find_start_code(): make the state parameter output only

[Scott Theisen]

---
 libavcodec/cbs_mpeg2.c                | 8 --------
 libavcodec/mpeg12dec.c                | 5 ++---
 libavcodec/mpeg4_unpack_bframes_bsf.c | 1 -
 libavcodec/mpegvideo_parser.c         | 3 +--
 libavcodec/utils.c                    | 1 +
 libavformat/rtpenc_mpv.c              | 3 +--
 6 files changed, 5 insertions(+), 16 deletions(-)

diff --git a/libavcodec/cbs_mpeg2.c b/libavcodec/cbs_mpeg2.c
index 26400f279f..03ea49cbca 100644
--- a/libavcodec/cbs_mpeg2.c
+++ b/libavcodec/cbs_mpeg2.c
@@ -160,14 +160,6 @@ static int cbs_mpeg2_split_fragment(CodedBitstreamContext *ctx,
     for (i = 0;; i++) {
         unit_type = start_code & 0xff;
 
-        if (start == frag->data + frag->data_size) {
-            // The last four bytes form a start code which constitutes
-            // a unit of its own.  In this situation avpriv_find_start_code
-            // won't modify start_code at all so modify start_code so that
-            // the next unit will be treated as the last unit.
-            start_code = 0;
-        }
-
         end = avpriv_find_start_code(start--, frag->data + frag->data_size,
                                      &start_code);
 
diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
index 4a7bd6d466..1110fcb319 100644
--- a/libavcodec/mpeg12dec.c
+++ b/libavcodec/mpeg12dec.c
@@ -1770,7 +1770,7 @@ static int mpeg_decode_slice(MpegEncContext *s, int mb_y,
 
     if (avctx->hwaccel && avctx->hwaccel->decode_slice) {
         const uint8_t *buf_end, *buf_start = *buf - 4; /* include start_code */
-        int start_code = -1;
+        uint32_t start_code;
         buf_end = avpriv_find_start_code(buf_start + 2, *buf + buf_size, &start_code);
         if (buf_end < *buf + buf_size)
             buf_end -= 4;
@@ -2020,7 +2020,6 @@ static int slice_decode_thread(AVCodecContext *c, void *arg)
         if (s->mb_y == s->end_mb_y)
             return 0;
 
-        start_code = -1;
         buf        = avpriv_find_start_code(buf, s->gb.buffer_end, &start_code);
         if (start_code < SLICE_MIN_START_CODE || start_code > SLICE_MAX_START_CODE)
             return AVERROR_INVALIDDATA;
@@ -2475,7 +2474,7 @@ static int decode_chunks(AVCodecContext *avctx, AVFrame *picture,
 
     for (;;) {
         /* find next start code */
-        uint32_t start_code = -1;
+        uint32_t start_code;
         buf_ptr = avpriv_find_start_code(buf_ptr, buf_end, &start_code);
         if (start_code > 0x1ff) {
             if (!skip_frame) {
diff --git a/libavcodec/mpeg4_unpack_bframes_bsf.c b/libavcodec/mpeg4_unpack_bframes_bsf.c
index 6f8595713d..8b3fda0b03 100644
--- a/libavcodec/mpeg4_unpack_bframes_bsf.c
+++ b/libavcodec/mpeg4_unpack_bframes_bsf.c
@@ -36,7 +36,6 @@ static void scan_buffer(const uint8_t *buf, int buf_size,
     const uint8_t *end = buf + buf_size, *pos = buf;
 
     while (pos < end) {
-        startcode = -1;
         pos = avpriv_find_start_code(pos, end, &startcode);
 
         if (startcode == USER_DATA_STARTCODE && pos_p) {
diff --git a/libavcodec/mpegvideo_parser.c b/libavcodec/mpegvideo_parser.c
index c5dc867d24..c991a82405 100644
--- a/libavcodec/mpegvideo_parser.c
+++ b/libavcodec/mpegvideo_parser.c
@@ -105,7 +105,6 @@ static void mpegvideo_extract_headers(AVCodecParserContext *s,
 {
     struct MpvParseContext *pc = s->priv_data;
     const uint8_t *buf_end = buf + buf_size;
-    uint32_t start_code;
     int frame_rate_index, ext_type, bytes_left;
     int frame_rate_ext_n, frame_rate_ext_d;
     int top_field_first, repeat_first_field, progressive_frame;
@@ -120,7 +119,7 @@ static void mpegvideo_extract_headers(AVCodecParserContext *s,
     s->repeat_pict = 0;
 
     while (buf < buf_end) {
-        start_code= -1;
+        uint32_t start_code;
         buf= avpriv_find_start_code(buf, buf_end, &start_code);
         bytes_left = buf_end - buf;
         switch(start_code) {
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 882f90be79..cf88e0a759 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -950,6 +950,7 @@ const uint8_t *avpriv_find_start_code(const uint8_t *av_restrict p,
     if (p >= end)
         return end;
 
+    *state = ~0;
     for (i = 0; i < 3; i++) {
         uint32_t tmp = *state << 8;
         *state = tmp + *(p++);
diff --git a/libavformat/rtpenc_mpv.c b/libavformat/rtpenc_mpv.c
index 4b45f51772..bb63c9bdc6 100644
--- a/libavformat/rtpenc_mpv.c
+++ b/libavformat/rtpenc_mpv.c
@@ -51,11 +51,10 @@ void ff_rtp_send_mpegvideo(AVFormatContext *s1, const uint8_t *buf1, int size)
             end_of_slice = 1;
         } else {
             const uint8_t *r, *r1;
-            int start_code;
 
             r1 = buf1;
             while (1) {
-                start_code = -1;
+                uint32_t start_code;
                 r = avpriv_find_start_code(r1, end, &start_code);
                 if((start_code & 0xFFFFFF00) == 0x100) {
                     /* New start code found */
-- 
2.32.0