libavcodec/adts_header: add frame_length field and avpriv function to parse AAC ADTS header

These will be used by HLS demuxer in case of sample decryption.

Signed-off-by: Nachiket Tarate <nachiket.programmer@gmail.com>
Signed-off-by: Steven Liu <lq@chinaffmpeg.org>

libavcodec/adts_header.c

@@ -66,6 +66,7 @@ int ff_adts_header_parse(GetBitContext *gbc, AACADTSHeaderInfo *hdr)
     hdr->sample_rate    = avpriv_mpeg4audio_sample_rates[sr];
     hdr->samples        = (rdb + 1) * 1024;
     hdr->bit_rate       = size * 8 * hdr->sample_rate / hdr->samples;
+    hdr->frame_length   = size;
 
     return size;
 }

libavcodec/adts_header.h

@@ -34,6 +34,7 @@ typedef struct AACADTSHeaderInfo {
     uint8_t  sampling_index;
     uint8_t  chan_config;
     uint8_t  num_aac_frames;
+    uint32_t frame_length;
 } AACADTSHeaderInfo;
 
 /**
@@ -47,4 +48,18 @@ typedef struct AACADTSHeaderInfo {
  */
 int ff_adts_header_parse(GetBitContext *gbc, AACADTSHeaderInfo *hdr);
 
+/**
+ * Parse the ADTS frame header contained in the buffer, which is
+ * the first 54 bits.
+ * @param[in]  buf  Pointer to buffer containing the first 54 bits of the frame.
+ * @param[in]  size Size of buffer containing the first 54 bits of the frame.
+ * @param[out] phdr Pointer to pointer to struct AACADTSHeaderInfo for which
+ * memory is allocated and header info is written into it. After using the header
+ * information, the allocated memory must be freed by using av_free.
+ * @return Returns 0 on success, -1 if there is a sync word mismatch,
+ * -2 if the version element is invalid, -3 if the sample rate
+ * element is invalid, or -4 if the bit rate element is invalid.
+ */
+int avpriv_adts_header_parse(AACADTSHeaderInfo **phdr, const uint8_t *buf, size_t size);
+
 #endif /* AVCODEC_ADTS_HEADER_H */

libavcodec/adts_parser.c

@@ -42,3 +42,34 @@ int av_adts_header_parse(const uint8_t *buf, uint32_t *samples, uint8_t *frames)
     return AVERROR(ENOSYS);
 #endif
 }
+
+int avpriv_adts_header_parse(AACADTSHeaderInfo **phdr, const uint8_t *buf, size_t size)
+{
+#if CONFIG_ADTS_HEADER
+    int ret = 0;
+    GetBitContext gb;
+
+    if (!phdr || !buf || size < AV_AAC_ADTS_HEADER_SIZE)
+        return AVERROR_INVALIDDATA;
+
+    *phdr = av_mallocz(sizeof(AACADTSHeaderInfo));
+    if (!*phdr)
+        return AVERROR(ENOMEM);
+
+    ret = init_get_bits8(&gb, buf, AV_AAC_ADTS_HEADER_SIZE);
+    if (ret < 0) {
+        av_freep(phdr);
+        return ret;
+    }
+
+    ret = ff_adts_header_parse(&gb, *phdr);
+    if (ret < 0) {
+        av_freep(phdr);
+        return ret;
+    }
+
+    return 0;
+#else
+    return AVERROR(ENOSYS);
+#endif
+}