aac: Set sample rate in avctx from ADTS header (if not already set by some

other means)

Originally committed as revision 20773 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/aac.c

@@ -1692,6 +1692,8 @@ static int parse_adts_frame_header(AACContext *ac, GetBitContext *gb)
         ac->m4ac.sample_rate     = hdr_info.sample_rate;
         ac->m4ac.sampling_index  = hdr_info.sampling_index;
         ac->m4ac.object_type     = hdr_info.object_type;
+        if (!ac->avccontext->sample_rate)
+            ac->avccontext->sample_rate = hdr_info.sample_rate;
         if (hdr_info.num_aac_frames == 1) {
             if (!hdr_info.crc_absent)
                 skip_bits(gb, 16);