avcodec/dca: remove GetBitContext usage from avpriv_dca_parse_core_frame_header()

This prevents potential ABI issues with GetBitContext.
Reviewed-by: foo86 <foobaz86@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/dca.c

@@ -88,7 +88,7 @@ int avpriv_dca_convert_bitstream(const uint8_t *src, int src_size, uint8_t *dst,
     }
 }
 
-int avpriv_dca_parse_core_frame_header(GetBitContext *gb, DCACoreFrameHeader *h)
+int ff_dca_parse_core_frame_header(DCACoreFrameHeader *h, GetBitContext *gb)
 {
     if (get_bits_long(gb, 32) != DCA_SYNCWORD_CORE_BE)
         return DCA_PARSE_ERROR_SYNC_WORD;
@@ -145,3 +145,13 @@ int avpriv_dca_parse_core_frame_header(GetBitContext *gb, DCACoreFrameHeader *h)
     h->dn_code = get_bits(gb, 4);
     return 0;
 }
+
+int avpriv_dca_parse_core_frame_header(DCACoreFrameHeader *h, uint8_t *buf, int size)
+{
+    GetBitContext gb;
+
+    if (init_get_bits8(&gb, buf, size) < 0)
+        return DCA_PARSE_ERROR_INVALIDDATA;
+
+    return ff_dca_parse_core_frame_header(h, &gb);
+}

libavcodec/dca.h

@@ -45,7 +45,8 @@ enum DCAParseError {
     DCA_PARSE_ERROR_SAMPLE_RATE     = -6,
     DCA_PARSE_ERROR_RESERVED_BIT    = -7,
     DCA_PARSE_ERROR_LFE_FLAG        = -8,
-    DCA_PARSE_ERROR_PCM_RES         = -9
+    DCA_PARSE_ERROR_PCM_RES         = -9,
+    DCA_PARSE_ERROR_INVALIDDATA     = -10,
 };
 
 typedef struct DCACoreFrameHeader {
@@ -212,6 +213,8 @@ int avpriv_dca_convert_bitstream(const uint8_t *src, int src_size, uint8_t *dst,
  * Parse and validate core frame header
  * @return 0 on success, negative DCA_PARSE_ERROR_ code on failure
  */
-int avpriv_dca_parse_core_frame_header(GetBitContext *gb, DCACoreFrameHeader *h);
+int avpriv_dca_parse_core_frame_header(DCACoreFrameHeader *h, uint8_t *buf, int size);
+
+int ff_dca_parse_core_frame_header(DCACoreFrameHeader *h, GetBitContext *gb);
 
 #endif /* AVCODEC_DCA_H */

libavcodec/dca_core.c

@@ -82,7 +82,7 @@ static void get_array(GetBitContext *s, int32_t *array, int size, int n)
 static int parse_frame_header(DCACoreDecoder *s)
 {
     DCACoreFrameHeader h = { 0 };
-    int err = avpriv_dca_parse_core_frame_header(&s->gb, &h);
+    int err = ff_dca_parse_core_frame_header(&h, &s->gb);
 
     if (err < 0) {
         switch (err) {

libavcodec/dca_parser.c

@@ -263,9 +263,7 @@ static int dca_parse_params(DCAParseContext *pc1, const uint8_t *buf,
     if ((ret = avpriv_dca_convert_bitstream(buf, DCA_CORE_FRAME_HEADER_SIZE,
                                             hdr, DCA_CORE_FRAME_HEADER_SIZE)) < 0)
         return ret;
-    if ((ret = init_get_bits8(&gb, hdr, ret)) < 0)
-        return ret;
-    if (avpriv_dca_parse_core_frame_header(&gb, &h) < 0)
+    if (avpriv_dca_parse_core_frame_header(&h, hdr, ret) < 0)
         return AVERROR_INVALIDDATA;
 
     *duration = h.npcmblocks * DCA_PCMBLOCK_SAMPLES;

libavformat/dtsdec.c

@@ -101,9 +101,7 @@ static int dts_probe(AVProbeData *p)
         if ((ret = avpriv_dca_convert_bitstream(buf - 2, DCA_CORE_FRAME_HEADER_SIZE,
                                                 hdr,     DCA_CORE_FRAME_HEADER_SIZE)) < 0)
             continue;
-        if (init_get_bits8(&gb, hdr, ret) < 0)
-            continue;
-        if (avpriv_dca_parse_core_frame_header(&gb, &h) < 0)
+        if (avpriv_dca_parse_core_frame_header(&h, hdr, ret) < 0)
             continue;
 
         marker += 4 * h.sr_code;