mov: add support for reading and writing the 'chan' tag

This implements reading the tag in the demuxer and adds support for writing it
in the muxer. Some example channel layout tables for muxing are included for
ac3, aac, and alac, but they are not utilized yet.

libavformat/Makefile

@@ -132,9 +132,10 @@ OBJS-$(CONFIG_MLP_MUXER)                 += rawenc.o
 OBJS-$(CONFIG_MM_DEMUXER)                += mm.o
 OBJS-$(CONFIG_MMF_DEMUXER)               += mmf.o pcm.o
 OBJS-$(CONFIG_MMF_MUXER)                 += mmf.o riff.o
-OBJS-$(CONFIG_MOV_DEMUXER)               += mov.o riff.o isom.o
+OBJS-$(CONFIG_MOV_DEMUXER)               += mov.o riff.o isom.o mov_chan.o
 OBJS-$(CONFIG_MOV_MUXER)                 += movenc.o riff.o isom.o avc.o \
-                                            movenchint.o rtpenc_chain.o
+                                            movenchint.o rtpenc_chain.o \
+                                            mov_chan.o
 OBJS-$(CONFIG_MP2_MUXER)                 += mp3enc.o rawenc.o
 OBJS-$(CONFIG_MP3_DEMUXER)               += mp3dec.o
 OBJS-$(CONFIG_MP3_MUXER)                 += mp3enc.o rawenc.o id3v2enc.o

libavformat/mov.c

@@ -37,6 +37,7 @@
 #include "isom.h"
 #include "libavcodec/get_bits.h"
 #include "id3v1.h"
+#include "mov_chan.h"
 
 #if CONFIG_ZLIB
 #include <zlib.h>
@@ -554,6 +555,51 @@ static int mov_read_dac3(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     return 0;
 }
 
+static int mov_read_chan(MOVContext *c, AVIOContext *pb, MOVAtom atom)
+{
+    AVStream *st;
+    uint8_t version;
+    uint32_t flags, layout_tag, bitmap, num_descr;
+
+    if (c->fc->nb_streams < 1)
+        return 0;
+    st = c->fc->streams[c->fc->nb_streams-1];
+
+    if (atom.size < 16)
+        return 0;
+
+    version = avio_r8(pb);
+    flags   = avio_rb24(pb);
+
+    layout_tag = avio_rb32(pb);
+    bitmap     = avio_rb32(pb);
+    num_descr  = avio_rb32(pb);
+
+    if (atom.size < 16ULL + num_descr * 20ULL)
+        return 0;
+
+    av_dlog(c->fc, "chan: size=%ld version=%u flags=%u layout=%u bitmap=%u num_descr=%u\n",
+            atom.size, version, flags, layout_tag, bitmap, num_descr);
+
+#if 0
+    /* TODO: use the channel descriptions if the layout tag is 0 */
+    int i;
+    for (i = 0; i < num_descr; i++) {
+        uint32_t label, cflags;
+        float coords[3];
+        label     = avio_rb32(pb);          // mChannelLabel
+        cflags    = avio_rb32(pb);          // mChannelFlags
+        AV_WN32(&coords[0], avio_rl32(pb)); // mCoordinates[0]
+        AV_WN32(&coords[1], avio_rl32(pb)); // mCoordinates[1]
+        AV_WN32(&coords[2], avio_rl32(pb)); // mCoordinates[2]
+    }
+#endif
+
+    st->codec->channel_layout = ff_mov_get_channel_layout(layout_tag, bitmap);
+
+    return 0;
+}
+
 static int mov_read_wfex(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 {
     AVStream *st;
@@ -2329,6 +2375,7 @@ static const MOVParseTableEntry mov_default_parse_table[] = {
 { MKTAG('w','i','d','e'), mov_read_wide }, /* place holder */
 { MKTAG('w','f','e','x'), mov_read_wfex },
 { MKTAG('c','m','o','v'), mov_read_cmov },
+{ MKTAG('c','h','a','n'), mov_read_chan }, /* channel layout */
 { 0, NULL }
 };
 

libavformat/mov_chan.h

+/*
+ * Copyright (c) 2011 Justin Ruggles
+ *
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * mov 'chan' tag reading/writing.
+ * @author Justin Ruggles
+ */
+
+#ifndef AVFORMAT_MOV_CHAN_H
+#define AVFORMAT_MOV_CHAN_H
+
+#include <stdint.h>
+
+#include "libavcodec/avcodec.h"
+
+/**
+ * Get the channel layout for the specified channel layout tag.
+ *
+ * @param[in]  tag     channel layout tag
+ * @param[out] bitmap  channel bitmap (only used if needed)
+ * @return             channel layout
+ */
+uint64_t ff_mov_get_channel_layout(uint32_t tag, uint32_t bitmap);
+
+/**
+ * Get the channel layout tag for the specified codec id and channel layout.
+ * If the layout tag was not found, use a channel bitmap if possible.
+ *
+ * @param[in]  codec_id        codec id
+ * @param[in]  channel_layout  channel layout
+ * @param[out] bitmap          channel bitmap
+ * @return                     channel layout tag
+ */
+uint32_t ff_mov_get_channel_layout_tag(enum CodecID codec_id,
+                                       uint64_t channel_layout,
+                                       uint32_t *bitmap);
+
+#endif /* AVFORMAT_MOV_CHAN_H */

libavformat/movenc.c

@@ -37,6 +37,7 @@
 #include "libavutil/opt.h"
 #include "libavutil/dict.h"
 #include "rtpenc.h"
+#include "mov_chan.h"
 
 #undef NDEBUG
 #include <assert.h>
@@ -338,6 +339,31 @@ static int mov_write_ms_tag(AVIOContext *pb, MOVTrack *track)
     return updateSize(pb, pos);
 }
 
+static int mov_write_chan_tag(AVIOContext *pb, MOVTrack *track)
+{
+    uint32_t layout_tag, bitmap;
+    int64_t pos = avio_tell(pb);
+
+    layout_tag = ff_mov_get_channel_layout_tag(track->enc->codec_id,
+                                               track->enc->channel_layout,
+                                               &bitmap);
+    if (!layout_tag) {
+        av_log(track->enc, AV_LOG_WARNING, "not writing 'chan' tag due to "
+               "lack of channel information\n");
+        return 0;
+    }
+
+    avio_wb32(pb, 0);           // Size
+    ffio_wfourcc(pb, "chan");   // Type
+    avio_w8(pb, 0);             // Version
+    avio_wb24(pb, 0);           // Flags
+    avio_wb32(pb, layout_tag);  // mChannelLayoutTag
+    avio_wb32(pb, bitmap);      // mChannelBitmap
+    avio_wb32(pb, 0);           // mNumberChannelDescriptions
+
+    return updateSize(pb, pos);
+}
+
 static int mov_write_wave_tag(AVIOContext *pb, MOVTrack *track)
 {
     int64_t pos = avio_tell(pb);