[FFmpeg-devel] [PATCH 03/10] spdifenc: handle prepadded DTS streams
Anssi Hannula
anssi.hannula
Wed Dec 29 06:06:36 CET 2010
Some DTS streams (like dts-in-wav or dts-in-disc) are already padded for
S/PDIF transmission by having their frame size set to exactly match the
S/PDIF bitrate. In this case, no preamble can be added, so do not add
it. (DTS is a special case and can be transmitted through S/PDIF without
the IEC 61937 headers)
---
libavformat/spdifenc.c | 13 ++++++++++++-
1 files changed, 12 insertions(+), 1 deletions(-)
diff --git a/libavformat/spdifenc.c b/libavformat/spdifenc.c
index 9f9db76..8b94459 100644
--- a/libavformat/spdifenc.c
+++ b/libavformat/spdifenc.c
@@ -60,6 +60,7 @@ typedef struct IEC958Context {
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 -1;
}
+ 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);
--
1.7.3
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