aaclatm: Eliminate dummy packets due to muxlength calculation.

Muxlength does not include the 3 bytes of AudioSyncStream() before the
AudioMuxElement(). If these three bytes are not accounted for the last three
bytes of the LATM packet are sent back to the decoder again.

Fixes issue244/mux2.share.ts

Originally committed as revision 25685 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/aacdec.c

@@ -2310,9 +2310,9 @@ static int latm_decode_frame(AVCodecContext *avctx, void *out, int *out_size,
     if (get_bits(&gb, 11) != LOAS_SYNC_WORD)
         return AVERROR_INVALIDDATA;
 
-    muxlength = get_bits(&gb, 13);
+    muxlength = get_bits(&gb, 13) + 3;
     // not enough data, the parser should have sorted this
-    if (muxlength+3 > avpkt->size)
+    if (muxlength > avpkt->size)
         return AVERROR_INVALIDDATA;
 
     if ((err = read_audio_mux_element(latmctx, &gb)) < 0)