[FFmpeg-devel] [PATCH v2 1/2] libavcodec/dnxhddec: refactor header prefix parsing

[Mark Reid]

---
 libavcodec/dnxhddata.c | 17 +++++++++++++++++
 libavcodec/dnxhddata.h | 11 +++++++++++
 libavcodec/dnxhddec.c  | 11 ++++-------
 3 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/libavcodec/dnxhddata.c b/libavcodec/dnxhddata.c
index 82fbfdf..5b909b6 100644
--- a/libavcodec/dnxhddata.c
+++ b/libavcodec/dnxhddata.c
@@ -23,6 +23,13 @@
 #include "dnxhddata.h"
 #include "libavutil/common.h"
 
+static const uint8_t dnxhd_headers[DNXHD_HEADER_VERSIONS][5] = {
+    { 0x00, 0x00, 0x02, 0x80, 0x01 },
+    { 0x00, 0x00, 0x02, 0x80, 0x02 },
+    { 0x00, 0x00, 0x02, 0x80, 0x03 },
+    { 0x00, 0x00, 0x03, 0x8C, 0x03 },
+};
+
 /* The quantization tables below are in zigzag order! */
 
 /* Used in CID 1235, 1256, 1270 */
@@ -1102,6 +1109,16 @@ int avpriv_dnxhd_get_interlaced(int cid)
     return ff_dnxhd_cid_table[i].flags & DNXHD_INTERLACED ? 1 : 0;
 }
 
+DNXHD_Header avpriv_dnxhd_parse_prefix(const uint8_t *buf)
+{
+  int i;
+  for (i = 0; i < DNXHD_HEADER_VERSIONS; i++) {
+    if (!memcmp(buf, dnxhd_headers[i], 5))
+      return i;
+  }
+  return DNXHD_HEADER_UNKNOWN;
+}
+
 int ff_dnxhd_find_cid(AVCodecContext *avctx, int bit_depth)
 {
     int i, j;
diff --git a/libavcodec/dnxhddata.h b/libavcodec/dnxhddata.h
index d973888..b388df8 100644
--- a/libavcodec/dnxhddata.h
+++ b/libavcodec/dnxhddata.h
@@ -34,6 +34,16 @@
 /** Indicate that a CIDEntry value must be read in the bitstream */
 #define DNXHD_VARIABLE 0
 
+/** Known header versions */
+typedef enum {
+    DNXHD_HEADER_INITIAL    = 0,
+    DNXHD_HEADER_444        = 1,
+    DNXHD_HEADER_HR1        = 2,
+    DNXHD_HEADER_HR2        = 3,
+    DNXHD_HEADER_VERSIONS,
+    DNXHD_HEADER_UNKNOWN
+} DNXHD_Header;
+
 typedef struct CIDEntry {
     int cid;
     unsigned int width, height;
@@ -61,5 +71,6 @@ void ff_dnxhd_print_profiles(AVCodecContext *avctx, int loglevel);
 
 int avpriv_dnxhd_get_frame_size(int cid);
 int avpriv_dnxhd_get_interlaced(int cid);
+DNXHD_Header avpriv_dnxhd_parse_prefix(const uint8_t *buf);
 
 #endif /* AVCODEC_DNXHDDATA_H */
diff --git a/libavcodec/dnxhddec.c b/libavcodec/dnxhddec.c
index 5c09c64..c111def 100644
--- a/libavcodec/dnxhddec.c
+++ b/libavcodec/dnxhddec.c
@@ -163,10 +163,6 @@ static int dnxhd_decode_header(DNXHDContext *ctx, AVFrame *frame,
                                const uint8_t *buf, int buf_size,
                                int first_field)
 {
-    static const uint8_t header_prefix[]    = { 0x00, 0x00, 0x02, 0x80, 0x01 };
-    static const uint8_t header_prefix444[] = { 0x00, 0x00, 0x02, 0x80, 0x02 };
-    static const uint8_t header_prefixhr1[] = { 0x00, 0x00, 0x02, 0x80, 0x03 };
-    static const uint8_t header_prefixhr2[] = { 0x00, 0x00, 0x03, 0x8C, 0x03 };
     int i, cid, ret;
     int old_bit_depth = ctx->bit_depth, bitdepth;
 
@@ -176,8 +172,9 @@ static int dnxhd_decode_header(DNXHDContext *ctx, AVFrame *frame,
         return AVERROR_INVALIDDATA;
     }
 
-    if (memcmp(buf, header_prefix, 5) && memcmp(buf, header_prefix444, 5) &&
-        memcmp(buf, header_prefixhr1, 5) && memcmp(buf, header_prefixhr2, 5)) {
+    DNXHD_Header header_prefix = avpriv_dnxhd_parse_prefix(buf);
+
+    if (header_prefix == DNXHD_HEADER_UNKNOWN) {
         av_log(ctx->avctx, AV_LOG_ERROR,
                "unknown header 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X\n",
                buf[0], buf[1], buf[2], buf[3], buf[4]);
@@ -279,7 +276,7 @@ static int dnxhd_decode_header(DNXHDContext *ctx, AVFrame *frame,
            ctx->bit_depth, ctx->mbaff, ctx->act);
 
     // Newer format supports variable mb_scan_index sizes
-    if (!memcmp(buf, header_prefixhr2, 5)) {
+    if (header_prefix == DNXHD_HEADER_HR2) {
         ctx->data_offset = 0x170 + (ctx->mb_height << 2);
     } else {
         if (ctx->mb_height > 68 ||
-- 
2.4.1