@@ -60,6 +60,7 @@ typedef struct IEC61937Context {

     uint8_t *out_buf;               ///< pointer to the outgoing data before byte-swapping

     int out_bytes;                  ///< amount of outgoing bytes

+    int use_preamble;               ///< preamble enabled (disabled for exactly pre-padded DTS)

     int extra_bswap;                ///< extra bswap for payload (for LE DTS => standard BE DTS)

     uint8_t *hd_buf;                ///< allocated buffer to concatenate hd audio frames

@@ -153,6 +154,13 @@ static int spdif_header_dts(AVFormatContext *s, AVPacket *pkt)

     }

     ctx->pkt_offset = blocks << 7;

+    if (ctx->out_bytes == ctx->pkt_offset) {

+        /* The DTS stream fits exactly into the output stream, so skip the

+         * preamble as it would not fit in there. This is the case for dts

+         * discs and dts-in-wav. */

+        ctx->use_preamble = 0;

+    }

+

     return 0;

 }

@@ -330,6 +338,7 @@ static int spdif_write_packet(struct AVFormatContext *s, AVPacket *pkt)

     ctx->out_buf = pkt->data;

     ctx->out_bytes = pkt->size;

     ctx->length_code = FFALIGN(pkt->size, 2) << 3;

+    ctx->use_preamble = 1;

     ctx->extra_bswap = 0;

     ret = ctx->header_info(s, pkt);

@@ -338,16 +347,18 @@ static int spdif_write_packet(struct AVFormatContext *s, AVPacket *pkt)

     if (!ctx->pkt_offset)

         return 0;

-    padding = (ctx->pkt_offset - BURST_HEADER_SIZE - ctx->out_bytes) >> 1;

+    padding = (ctx->pkt_offset - ctx->use_preamble * BURST_HEADER_SIZE - ctx->out_bytes) >> 1;

     if (padding < 0) {

         av_log(s, AV_LOG_ERROR, "bitrate is too high\n");

         return AVERROR(EINVAL);

     }

+    if (ctx->use_preamble) {

     put_le16(s->pb, SYNCWORD1);      //Pa

     put_le16(s->pb, SYNCWORD2);      //Pb

     put_le16(s->pb, ctx->data_type); //Pc

     put_le16(s->pb, ctx->length_code);//Pd

+    }

     if (HAVE_BIGENDIAN ^ ctx->extra_bswap) {

     put_buffer(s->pb, ctx->out_buf, ctx->out_bytes & ~1);