[PATCH] libavformat: add S/PDIF demuxer

Anssi Hannula anssi.hannula
Fri Jul 23 04:52:03 CEST 2010


---
 doc/general.texi         |    2 +
 libavformat/Makefile     |    1 +
 libavformat/allformats.c |    2 +-
 libavformat/spdif.c      |  196 +++++++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 199 insertions(+), 2 deletions(-)

diff --git a/doc/general.texi b/doc/general.texi
index 76c676f..eefbdb5 100644
--- a/doc/general.texi
+++ b/doc/general.texi
@@ -228,6 +228,8 @@ library:
 @item Sony PlayStation STR      @tab   @tab X
 @item Sony Wave64 (W64)         @tab   @tab X
 @item SoX native format         @tab X @tab X
+ at item S/PDIF / IEC958 (IEC-61937) @tab X @tab X
+    @tab Encoded data encapsulated in IEC-61937 as used in S/PDIF.
 @item SUN AU format             @tab X @tab X
 @item Text files                @tab   @tab X
 @item THP                       @tab   @tab X
diff --git a/libavformat/Makefile b/libavformat/Makefile
index 50a7b3a..5526d36 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -241,6 +241,7 @@ OBJS-$(CONFIG_SMACKER_DEMUXER)           += smacker.o
 OBJS-$(CONFIG_SOL_DEMUXER)               += sol.o raw.o
 OBJS-$(CONFIG_SOX_DEMUXER)               += soxdec.o raw.o
 OBJS-$(CONFIG_SOX_MUXER)                 += soxenc.o
+OBJS-$(CONFIG_SPDIF_DEMUXER)             += spdif.o
 OBJS-$(CONFIG_SPDIF_MUXER)               += spdif.o
 OBJS-$(CONFIG_STR_DEMUXER)               += psxstr.o
 OBJS-$(CONFIG_SWF_DEMUXER)               += swfdec.o
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index ce0e90d..d7c657e 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -188,7 +188,7 @@ void av_register_all(void)
     REGISTER_DEMUXER  (SMACKER, smacker);
     REGISTER_DEMUXER  (SOL, sol);
     REGISTER_MUXDEMUX (SOX, sox);
-    REGISTER_MUXER    (SPDIF, spdif);
+    REGISTER_MUXDEMUX (SPDIF, spdif);
     REGISTER_DEMUXER  (STR, str);
     REGISTER_MUXDEMUX (SWF, swf);
     REGISTER_MUXER    (TG2, tg2);
diff --git a/libavformat/spdif.c b/libavformat/spdif.c
index ac84c50..5bc692a 100644
--- a/libavformat/spdif.c
+++ b/libavformat/spdif.c
@@ -1,6 +1,7 @@
 /*
- * IEC958 muxer
+ * IEC958 muxer and demuxer
  * Copyright (c) 2009 Bartlomiej Wolowiec
+ * Copyright (c) 2010 Anssi Hannula <anssi.hannula at iki.fi>
  *
  * This file is part of FFmpeg.
  *
@@ -23,6 +24,7 @@
  * @file
  * IEC-61937 encapsulation of various formats, used by S/PDIF
  * @author Bartlomiej Wolowiec
+ * @author Anssi Hannula
  */
 
 /*
@@ -103,6 +105,7 @@ static void bswap_buf16(uint16_t *dst, const uint16_t *src, int w)
         dst[i + 0] = av_bswap16(src[i + 0]);
 }
 
+#if CONFIG_SPDIF_MUXER
 static int spdif_header_ac3(AVFormatContext *s, AVPacket *pkt)
 {
     IEC958Context *ctx = s->priv_data;
@@ -158,6 +161,7 @@ static const enum IEC958DataType mpeg_data_type[2][3] = {
     { IEC958_MPEG2_LAYER1_LSF, IEC958_MPEG2_LAYER2_LSF, IEC958_MPEG2_LAYER3_LSF },  //MPEG2 LSF
     { IEC958_MPEG1_LAYER1,     IEC958_MPEG1_LAYER23,    IEC958_MPEG1_LAYER23 },     //MPEG1
 };
+#endif
 
 static const uint16_t mpeg_pkt_offset[2][3] = {
     //LAYER1  LAYER2  LAYER3
@@ -165,6 +169,7 @@ static const uint16_t mpeg_pkt_offset[2][3] = {
     { 1536,    4608,   4608 }, // MPEG1
 };
 
+#if CONFIG_SPDIF_MUXER
 static int spdif_header_mpeg(AVFormatContext *s, AVPacket *pkt)
 {
     IEC958Context *ctx = s->priv_data;
@@ -311,3 +316,192 @@ AVOutputFormat spdif_muxer = {
     spdif_write_packet,
     spdif_write_trailer,
 };
+#endif
+
+#if CONFIG_SPDIF_DEMUXER
+
+/* Largest offset between bursts we currently handle, i.e. AAC with
+   aac_hdr.samples = 4096 */
+#define SPDIF_MAX_OFFSET 16384
+
+static int spdif_probe(AVProbeData *p)
+{
+    const uint8_t *buf = p->buf;
+    const uint8_t *probe_end = p->buf + FFMIN(64, p->buf_size) - 1;
+    const uint8_t *prev_sync = NULL;
+    uint32_t state = 0;
+    int sync_codes = 0;
+
+    for (; buf < probe_end; buf++) {
+        state = (state << 8) | *buf;
+
+        if (state == (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))) {
+            if (buf == p->buf + 7)
+                return AVPROBE_SCORE_MAX; /* sync word at the very beginning */
+            if (++sync_codes >= 4)
+                return AVPROBE_SCORE_MAX; /* 4 sync codes found */
+
+            prev_sync = buf;
+            if (sync_codes == 1)
+                /* continue probing to find more sync codes */
+                probe_end = p->buf + p->buf_size;
+            continue;
+        }
+        if (prev_sync && buf > prev_sync + SPDIF_MAX_OFFSET)
+            return 1; /* at least one sync code found, but there is a gap */
+    }
+
+    if (sync_codes) {
+        /* sync codes were found, but buffer ended before 4 sync codes were
+           encountered; we still return relatively high score so that
+           (ac3-in-)spdif-in-wav gets probed as spdif as chained demuxers are
+           not yet supported */
+        return AVPROBE_SCORE_MAX - 1;
+    }
+    return 0;
+}
+
+static int spdif_read_header(AVFormatContext *s, AVFormatParameters *ap)
+{
+    s->ctx_flags |= AVFMTCTX_NOHEADER;
+    return 0;
+}
+
+static int spdif_get_offset_and_codec(enum IEC958DataType data_type,
+                                      AVPacket *pkt, int *offset,
+                                      enum CodecID *codec,
+                                      AVFormatContext *s)
+{
+    AACADTSHeaderInfo aac_hdr;
+    GetBitContext gbc;
+
+    switch (data_type & 0xff) {
+    case IEC958_AC3:
+        *offset = AC3_FRAME_SIZE << 2;
+        *codec = CODEC_ID_AC3;
+        break;
+    case IEC958_MPEG1_LAYER1:
+        *offset = mpeg_pkt_offset[1][0];
+        *codec = CODEC_ID_MP1;
+        break;
+    case IEC958_MPEG1_LAYER23:
+        *offset = mpeg_pkt_offset[1][0];
+        *codec = CODEC_ID_MP3;
+        break;
+    case IEC958_MPEG2_EXT:
+        *offset = 4608;
+        *codec = CODEC_ID_MP3;
+        break;
+    case IEC958_MPEG2_AAC:
+        init_get_bits(&gbc, pkt->data, AAC_ADTS_HEADER_SIZE * 8);
+        if (ff_aac_parse_header(&gbc, &aac_hdr)) {
+            av_log(s, AV_LOG_ERROR, "Invalid AAC packet in S/PDIF\n");
+            return AVERROR(EINVAL);
+        }
+        *offset = aac_hdr.samples << 2;
+        *codec = CODEC_ID_AAC;
+        break;
+    case IEC958_MPEG2_LAYER1_LSF:
+        *offset = mpeg_pkt_offset[0][0];
+        *codec = CODEC_ID_MP1;
+        break;
+    case IEC958_MPEG2_LAYER2_LSF:
+        *offset = mpeg_pkt_offset[0][1];
+        *codec = CODEC_ID_MP2;
+        break;
+    case IEC958_MPEG2_LAYER3_LSF:
+        *offset = mpeg_pkt_offset[0][2];
+        *codec = CODEC_ID_MP3;
+        break;
+    case IEC958_DTS1:
+        *offset = 2048;
+        *codec = CODEC_ID_DTS;
+        break;
+    case IEC958_DTS2:
+        *offset = 4096;
+        *codec = CODEC_ID_DTS;
+        break;
+    case IEC958_DTS3:
+        *offset = 8192;
+        *codec = CODEC_ID_DTS;
+        break;
+    default:
+        av_log(s, AV_LOG_WARNING, "Data type 0x%04x", data_type);
+        av_log_missing_feature(s, " in S/PDIF is", 1);
+        return AVERROR(ENOSYS);
+    }
+    return 0;
+}
+
+static int spdif_read_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    ByteIOContext *pb = s->pb;
+    enum IEC958DataType data_type;
+    enum CodecID codec_id;
+    uint32_t state = 0;
+    int pkt_size_bits, offset, ret;
+
+    while (state != (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))) {
+        state = (state << 8) | get_byte(pb);
+        if (url_feof(pb))
+            return AVERROR_EOF;
+    }
+
+    data_type = get_le16(pb);
+    pkt_size_bits = get_le16(pb);
+
+    if (pkt_size_bits % 16)
+        av_log_ask_for_sample(s, "Packet does not end to a 16-bit boundary.");
+
+    ret = av_new_packet(pkt, FFALIGN(pkt_size_bits, 16) >> 3);
+    if (ret)
+        return ret;
+
+    pkt->pos = url_ftell(pb) - BURST_HEADER_SIZE;
+
+    if (get_buffer(pb, pkt->data, pkt->size) < pkt->size) {
+        av_free_packet(pkt);
+        return AVERROR(EIO);
+    }
+    bswap_buf16((uint16_t *)pkt->data, (uint16_t *)pkt->data, pkt->size >> 1);
+
+    ret = spdif_get_offset_and_codec(data_type, pkt, &offset, &codec_id, s);
+    if (ret) {
+        av_free_packet(pkt);
+        return ret;
+    }
+
+    /* skip over the padding to the beginning of the next frame */
+    url_fskip(pb, offset - pkt->size - BURST_HEADER_SIZE);
+
+    if (!s->nb_streams) {
+        /* first packet, create a stream */
+        AVStream *st = av_new_stream(s, 0);
+        if (!st) {
+            av_free_packet(pkt);
+            return AVERROR(ENOMEM);
+        }
+        st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
+        st->codec->codec_id = codec_id;
+    } else if (codec_id != s->streams[0]->codec->codec_id) {
+        av_log_ask_for_sample(s, "Codec changed in S/PDIF stream.");
+        return AVERROR(ENOSYS);
+    }
+
+    if (!s->bit_rate && s->streams[0]->codec->sample_rate)
+        /* stream bitrate matches 16-bit stereo PCM bitrate */
+        s->bit_rate = 2 * 16 * s->streams[0]->codec->sample_rate;
+
+    return 0;
+}
+
+AVInputFormat spdif_demuxer = {
+    "spdif",
+    NULL_IF_CONFIG_SMALL("IEC958 - S/PDIF (IEC-61937)"),
+    0,
+    spdif_probe,
+    spdif_read_header,
+    spdif_read_packet,
+    .flags = AVFMT_GENERIC_INDEX,
+};
+#endif
-- 
1.7.1


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