riff: Move muxing code to a separate file

4 files changed, 307 insertions, 270 deletions

diff --git a/configure b/configure
index fe33e78717..dbead9def3 100755
--- a/configure
+++ b/configure
@@ -1390,6 +1390,7 @@ CONFIG_EXTRA="
     mpegvideoenc
     nettle
     rangecoder
+    riffenc
     rtpdec
     rtpenc_chain
     sinewin
@@ -1791,7 +1792,9 @@ libxvid_encoder_deps="libxvid"
 
 # demuxers / muxers
 ac3_demuxer_select="ac3_parser"
+asf_muxer_select="riffenc"
 asf_stream_muxer_select="asf_muxer"
+avi_muxer_select="riffenc"
 avisynth_demuxer_deps="avisynth"
 dirac_demuxer_select="dirac_parser"
 eac3_demuxer_select="ac3_parser"
@@ -1800,13 +1803,16 @@ ipod_muxer_select="mov_muxer"
 ismv_muxer_select="mov_muxer"
 matroska_audio_muxer_select="matroska_muxer"
 matroska_demuxer_suggest="bzlib lzo zlib"
+matroska_muxer_select="riffenc"
+mmf_muxer_select="riffenc"
 mov_demuxer_suggest="zlib"
-mov_muxer_select="rtpenc_chain"
+mov_muxer_select="riffenc rtpenc_chain"
 mp3_demuxer_select="mpegaudio_parser"
 mp4_muxer_select="mov_muxer"
 mpegts_muxer_select="adts_muxer latm_muxer"
 mpegtsraw_demuxer_select="mpegts_demuxer"
 mxf_d10_muxer_select="mxf_muxer"
+nut_muxer_select="riffenc"
 ogg_demuxer_select="golomb"
 psp_muxer_select="mov_muxer"
 rtp_demuxer_select="sdp_demuxer"
@@ -1822,6 +1828,8 @@ tak_demuxer_select="tak_parser"
 tg2_muxer_select="mov_muxer"
 tgp_muxer_select="mov_muxer"
 w64_demuxer_deps="wav_demuxer"
+wav_muxer_select="riffenc"
+webm_muxer_select="riffenc"
 
 # indevs / outdevs
 alsa_indev_deps="alsa_asoundlib_h snd_pcm_htimestamp"
diff --git a/libavformat/Makefile b/libavformat/Makefile
index 9624aeca46..a68f6061f3 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -24,6 +24,7 @@ OBJS = allformats.o         \
        utils.o              \
 
 OBJS-$(CONFIG_NETWORK)                   += network.o
+OBJS-$(CONFIG_RIFFENC)                   += riffenc.o
 OBJS-$(CONFIG_RTPDEC)                    += rdt.o                       \
                                             rtp.o                       \
                                             rtpdec.o                    \
diff --git a/libavformat/riff.c b/libavformat/riff.c
index 3f1790e9d0..fdee064b80 100644
--- a/libavformat/riff.c
+++ b/libavformat/riff.c
@@ -19,7 +19,8 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-#include "libavutil/mathematics.h"
+#include "libavutil/error.h"
+#include "libavutil/log.h"
 #include "libavcodec/avcodec.h"
 #include "avformat.h"
 #include "avio_internal.h"
@@ -421,274 +422,6 @@ const struct AVCodecTag *avformat_get_riff_audio_tags(void)
     return ff_codec_wav_tags;
 }
 
-#if CONFIG_MUXERS
-int64_t ff_start_tag(AVIOContext *pb, const char *tag)
-{
-    ffio_wfourcc(pb, tag);
-    avio_wl32(pb, 0);
-    return avio_tell(pb);
-}
-
-void ff_end_tag(AVIOContext *pb, int64_t start)
-{
-    int64_t pos;
-
-    pos = avio_tell(pb);
-    avio_seek(pb, start - 4, SEEK_SET);
-    avio_wl32(pb, (uint32_t)(pos - start));
-    avio_seek(pb, pos, SEEK_SET);
-}
-
-/* WAVEFORMATEX header */
-/* returns the size or -1 on error */
-int ff_put_wav_header(AVIOContext *pb, AVCodecContext *enc)
-{
-    int bps, blkalign, bytespersec, frame_size;
-    int hdrsize = 18;
-    int waveformatextensible;
-    uint8_t temp[256];
-    uint8_t *riff_extradata       = temp;
-    uint8_t *riff_extradata_start = temp;
-
-    if (!enc->codec_tag || enc->codec_tag > 0xffff)
-        return -1;
-
-    /* We use the known constant frame size for the codec if known, otherwise
-     * fall back on using AVCodecContext.frame_size, which is not as reliable
-     * for indicating packet duration. */
-    frame_size = av_get_audio_frame_duration(enc, 0);
-    if (!frame_size)
-        frame_size = enc->frame_size;
-
-    waveformatextensible = (enc->channels > 2 && enc->channel_layout) ||
-                           enc->sample_rate > 48000 ||
-                           av_get_bits_per_sample(enc->codec_id) > 16;
-
-    if (waveformatextensible)
-        avio_wl16(pb, 0xfffe);
-    else
-        avio_wl16(pb, enc->codec_tag);
-
-    avio_wl16(pb, enc->channels);
-    avio_wl32(pb, enc->sample_rate);
-    if (enc->codec_id == AV_CODEC_ID_MP2 ||
-        enc->codec_id == AV_CODEC_ID_MP3 ||
-        enc->codec_id == AV_CODEC_ID_GSM_MS) {
-        bps = 0;
-    } else {
-        if (!(bps = av_get_bits_per_sample(enc->codec_id))) {
-            if (enc->bits_per_coded_sample)
-                bps = enc->bits_per_coded_sample;
-            else
-                bps = 16;  // default to 16
-        }
-    }
-    if (bps != enc->bits_per_coded_sample && enc->bits_per_coded_sample) {
-        av_log(enc, AV_LOG_WARNING,
-               "requested bits_per_coded_sample (%d) "
-               "and actually stored (%d) differ\n",
-               enc->bits_per_coded_sample, bps);
-    }
-
-    if (enc->codec_id == AV_CODEC_ID_MP2 ||
-        enc->codec_id == AV_CODEC_ID_MP3) {
-        /* This is wrong, but it seems many demuxers do not work if this
-         * is set correctly. */
-        blkalign = frame_size;
-        // blkalign = 144 * enc->bit_rate/enc->sample_rate;
-    } else if (enc->codec_id == AV_CODEC_ID_AC3) {
-        blkalign = 3840;                /* maximum bytes per frame */
-    } else if (enc->block_align != 0) { /* specified by the codec */
-        blkalign = enc->block_align;
-    } else
-        blkalign = bps * enc->channels / av_gcd(8, bps);
-    if (enc->codec_id == AV_CODEC_ID_PCM_U8 ||
-        enc->codec_id == AV_CODEC_ID_PCM_S24LE ||
-        enc->codec_id == AV_CODEC_ID_PCM_S32LE ||
-        enc->codec_id == AV_CODEC_ID_PCM_F32LE ||
-        enc->codec_id == AV_CODEC_ID_PCM_F64LE ||
-        enc->codec_id == AV_CODEC_ID_PCM_S16LE) {
-        bytespersec = enc->sample_rate * blkalign;
-    } else {
-        bytespersec = enc->bit_rate / 8;
-    }
-    avio_wl32(pb, bytespersec); /* bytes per second */
-    avio_wl16(pb, blkalign);    /* block align */
-    avio_wl16(pb, bps);         /* bits per sample */
-    if (enc->codec_id == AV_CODEC_ID_MP3) {
-        hdrsize += 12;
-        bytestream_put_le16(&riff_extradata, 1);    /* wID */
-        bytestream_put_le32(&riff_extradata, 2);    /* fdwFlags */
-        bytestream_put_le16(&riff_extradata, 1152); /* nBlockSize */
-        bytestream_put_le16(&riff_extradata, 1);    /* nFramesPerBlock */
-        bytestream_put_le16(&riff_extradata, 1393); /* nCodecDelay */
-    } else if (enc->codec_id == AV_CODEC_ID_MP2) {
-        hdrsize += 22;
-        /* fwHeadLayer */
-        bytestream_put_le16(&riff_extradata, 2);
-        /* dwHeadBitrate */
-        bytestream_put_le32(&riff_extradata, enc->bit_rate);
-        /* fwHeadMode */
-        bytestream_put_le16(&riff_extradata, enc->channels == 2 ? 1 : 8);
-        /* fwHeadModeExt */
-        bytestream_put_le16(&riff_extradata, 0);
-        /* wHeadEmphasis */
-        bytestream_put_le16(&riff_extradata, 1);
-        /* fwHeadFlags */
-        bytestream_put_le16(&riff_extradata, 16);
-        /* dwPTSLow */
-        bytestream_put_le32(&riff_extradata, 0);
-        /* dwPTSHigh */
-        bytestream_put_le32(&riff_extradata, 0);
-    } else if (enc->codec_id == AV_CODEC_ID_GSM_MS ||
-               enc->codec_id == AV_CODEC_ID_ADPCM_IMA_WAV) {
-        hdrsize += 2;
-        /* wSamplesPerBlock */
-        bytestream_put_le16(&riff_extradata, frame_size);
-    } else if (enc->extradata_size) {
-        riff_extradata_start = enc->extradata;
-        riff_extradata       = enc->extradata + enc->extradata_size;
-        hdrsize             += enc->extradata_size;
-    }
-    /* write WAVEFORMATEXTENSIBLE extensions */
-    if (waveformatextensible) {
-        hdrsize += 22;
-        /* 22 is WAVEFORMATEXTENSIBLE size */
-        avio_wl16(pb, riff_extradata - riff_extradata_start + 22);
-        /* ValidBitsPerSample || SamplesPerBlock || Reserved */
-        avio_wl16(pb, bps);
-        /* dwChannelMask */
-        avio_wl32(pb, enc->channel_layout);
-        /* GUID + next 3 */
-        avio_wl32(pb, enc->codec_tag);
-        avio_wl32(pb, 0x00100000);
-        avio_wl32(pb, 0xAA000080);
-        avio_wl32(pb, 0x719B3800);
-    } else {
-        avio_wl16(pb, riff_extradata - riff_extradata_start); /* cbSize */
-    }
-    avio_write(pb, riff_extradata_start, riff_extradata - riff_extradata_start);
-    if (hdrsize & 1) {
-        hdrsize++;
-        avio_w8(pb, 0);
-    }
-
-    return hdrsize;
-}
-
-/* BITMAPINFOHEADER header */
-void ff_put_bmp_header(AVIOContext *pb, AVCodecContext *enc,
-                       const AVCodecTag *tags, int for_asf)
-{
-    /* size */
-    avio_wl32(pb, 40 + enc->extradata_size);
-    avio_wl32(pb, enc->width);
-    //We always store RGB TopDown
-    avio_wl32(pb, enc->codec_tag ? enc->height : -enc->height);
-    /* planes */
-    avio_wl16(pb, 1);
-    /* depth */
-    avio_wl16(pb, enc->bits_per_coded_sample ? enc->bits_per_coded_sample : 24);
-    /* compression type */
-    avio_wl32(pb, enc->codec_tag);
-    avio_wl32(pb, enc->width * enc->height * 3);
-    avio_wl32(pb, 0);
-    avio_wl32(pb, 0);
-    avio_wl32(pb, 0);
-    avio_wl32(pb, 0);
-
-    avio_write(pb, enc->extradata, enc->extradata_size);
-
-    if (!for_asf && enc->extradata_size & 1)
-        avio_w8(pb, 0);
-}
-
-void ff_parse_specific_params(AVCodecContext *stream, int *au_rate,
-                              int *au_ssize, int *au_scale)
-{
-    int gcd;
-    int audio_frame_size;
-
-    /* We use the known constant frame size for the codec if known, otherwise
-     * fall back on using AVCodecContext.frame_size, which is not as reliable
-     * for indicating packet duration. */
-    audio_frame_size = av_get_audio_frame_duration(stream, 0);
-    if (!audio_frame_size)
-        audio_frame_size = stream->frame_size;
-
-    *au_ssize = stream->block_align;
-    if (audio_frame_size && stream->sample_rate) {
-        *au_scale = audio_frame_size;
-        *au_rate  = stream->sample_rate;
-    } else if (stream->codec_type == AVMEDIA_TYPE_VIDEO ||
-               stream->codec_type == AVMEDIA_TYPE_DATA ||
-               stream->codec_type == AVMEDIA_TYPE_SUBTITLE) {
-        *au_scale = stream->time_base.num;
-        *au_rate  = stream->time_base.den;
-    } else {
-        *au_scale = stream->block_align ? stream->block_align * 8 : 8;
-        *au_rate  = stream->bit_rate ? stream->bit_rate :
-                    8 * stream->sample_rate;
-    }
-    gcd        = av_gcd(*au_scale, *au_rate);
-    *au_scale /= gcd;
-    *au_rate  /= gcd;
-}
-
-void ff_riff_write_info_tag(AVIOContext *pb, const char *tag, const char *str)
-{
-    int len = strlen(str);
-    if (len > 0) {
-        len++;
-        ffio_wfourcc(pb, tag);
-        avio_wl32(pb, len);
-        avio_put_str(pb, str);
-        if (len & 1)
-            avio_w8(pb, 0);
-    }
-}
-
-static const char riff_tags[][5] = {
-    "IARL", "IART", "ICMS", "ICMT", "ICOP", "ICRD", "ICRP", "IDIM", "IDPI",
-    "IENG", "IGNR", "IKEY", "ILGT", "ILNG", "IMED", "INAM", "IPLT", "IPRD",
-    "IPRT", "ISBJ", "ISFT", "ISHP", "ISRC", "ISRF", "ITCH",
-    { 0 }
-};
-
-static int riff_has_valid_tags(AVFormatContext *s)
-{
-    int i;
-
-    for (i = 0; *riff_tags[i]; i++)
-        if (av_dict_get(s->metadata, riff_tags[i], NULL, AV_DICT_MATCH_CASE))
-            return 1;
-
-    return 0;
-}
-
-void ff_riff_write_info(AVFormatContext *s)
-{
-    AVIOContext *pb = s->pb;
-    int i;
-    int64_t list_pos;
-    AVDictionaryEntry *t = NULL;
-
-    ff_metadata_conv(&s->metadata, ff_riff_info_conv, NULL);
-
-    /* writing empty LIST is not nice and may cause problems */
-    if (!riff_has_valid_tags(s))
-        return;
-
-    list_pos = ff_start_tag(pb, "LIST");
-    ffio_wfourcc(pb, "INFO");
-    for (i = 0; *riff_tags[i]; i++)
-        if ((t = av_dict_get(s->metadata, riff_tags[i],
-                             NULL, AV_DICT_MATCH_CASE)))
-            ff_riff_write_info_tag(s->pb, t->key, t->value);
-    ff_end_tag(pb, list_pos);
-}
-#endif /* CONFIG_MUXERS */
-
 #if CONFIG_DEMUXERS
 /* We could be given one of the three possible structures here:
  * WAVEFORMAT, PCMWAVEFORMAT or WAVEFORMATEX. Each structure
diff --git a/libavformat/riffenc.c b/libavformat/riffenc.c
new file mode 100644
index 0000000000..98e97c05ed
--- /dev/null
+++ b/libavformat/riffenc.c
@@ -0,0 +1,295 @@
+/*
+ * RIFF muxing functions
+ * Copyright (c) 2000 Fabrice Bellard
+ *
+ * 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
+ */
+
+#include "libavutil/dict.h"
+#include "libavutil/log.h"
+#include "libavutil/mathematics.h"
+#include "libavcodec/avcodec.h"
+#include "libavcodec/bytestream.h"
+#include "avformat.h"
+#include "avio_internal.h"
+#include "riff.h"
+
+int64_t ff_start_tag(AVIOContext *pb, const char *tag)
+{
+    ffio_wfourcc(pb, tag);
+    avio_wl32(pb, 0);
+    return avio_tell(pb);
+}
+
+void ff_end_tag(AVIOContext *pb, int64_t start)
+{
+    int64_t pos;
+
+    pos = avio_tell(pb);
+    avio_seek(pb, start - 4, SEEK_SET);
+    avio_wl32(pb, (uint32_t)(pos - start));
+    avio_seek(pb, pos, SEEK_SET);
+}
+
+/* WAVEFORMATEX header */
+/* returns the size or -1 on error */
+int ff_put_wav_header(AVIOContext *pb, AVCodecContext *enc)
+{
+    int bps, blkalign, bytespersec, frame_size;
+    int hdrsize = 18;
+    int waveformatextensible;
+    uint8_t temp[256];
+    uint8_t *riff_extradata       = temp;
+    uint8_t *riff_extradata_start = temp;
+
+    if (!enc->codec_tag || enc->codec_tag > 0xffff)
+        return -1;
+
+    /* We use the known constant frame size for the codec if known, otherwise
+     * fall back on using AVCodecContext.frame_size, which is not as reliable
+     * for indicating packet duration. */
+    frame_size = av_get_audio_frame_duration(enc, 0);
+    if (!frame_size)
+        frame_size = enc->frame_size;
+
+    waveformatextensible = (enc->channels > 2 && enc->channel_layout) ||
+                           enc->sample_rate > 48000 ||
+                           av_get_bits_per_sample(enc->codec_id) > 16;
+
+    if (waveformatextensible)
+        avio_wl16(pb, 0xfffe);
+    else
+        avio_wl16(pb, enc->codec_tag);
+
+    avio_wl16(pb, enc->channels);
+    avio_wl32(pb, enc->sample_rate);
+    if (enc->codec_id == AV_CODEC_ID_MP2 ||
+        enc->codec_id == AV_CODEC_ID_MP3 ||
+        enc->codec_id == AV_CODEC_ID_GSM_MS) {
+        bps = 0;
+    } else {
+        if (!(bps = av_get_bits_per_sample(enc->codec_id))) {
+            if (enc->bits_per_coded_sample)
+                bps = enc->bits_per_coded_sample;
+            else
+                bps = 16;  // default to 16
+        }
+    }
+    if (bps != enc->bits_per_coded_sample && enc->bits_per_coded_sample) {
+        av_log(enc, AV_LOG_WARNING,
+               "requested bits_per_coded_sample (%d) "
+               "and actually stored (%d) differ\n",
+               enc->bits_per_coded_sample, bps);
+    }
+
+    if (enc->codec_id == AV_CODEC_ID_MP2 ||
+        enc->codec_id == AV_CODEC_ID_MP3) {
+        /* This is wrong, but it seems many demuxers do not work if this
+         * is set correctly. */
+        blkalign = frame_size;
+        // blkalign = 144 * enc->bit_rate/enc->sample_rate;
+    } else if (enc->codec_id == AV_CODEC_ID_AC3) {
+        blkalign = 3840;                /* maximum bytes per frame */
+    } else if (enc->block_align != 0) { /* specified by the codec */
+        blkalign = enc->block_align;
+    } else
+        blkalign = bps * enc->channels / av_gcd(8, bps);
+    if (enc->codec_id == AV_CODEC_ID_PCM_U8 ||
+        enc->codec_id == AV_CODEC_ID_PCM_S24LE ||
+        enc->codec_id == AV_CODEC_ID_PCM_S32LE ||
+        enc->codec_id == AV_CODEC_ID_PCM_F32LE ||
+        enc->codec_id == AV_CODEC_ID_PCM_F64LE ||
+        enc->codec_id == AV_CODEC_ID_PCM_S16LE) {
+        bytespersec = enc->sample_rate * blkalign;
+    } else {
+        bytespersec = enc->bit_rate / 8;
+    }
+    avio_wl32(pb, bytespersec); /* bytes per second */
+    avio_wl16(pb, blkalign);    /* block align */
+    avio_wl16(pb, bps);         /* bits per sample */
+    if (enc->codec_id == AV_CODEC_ID_MP3) {
+        hdrsize += 12;
+        bytestream_put_le16(&riff_extradata, 1);    /* wID */
+        bytestream_put_le32(&riff_extradata, 2);    /* fdwFlags */
+        bytestream_put_le16(&riff_extradata, 1152); /* nBlockSize */
+        bytestream_put_le16(&riff_extradata, 1);    /* nFramesPerBlock */
+        bytestream_put_le16(&riff_extradata, 1393); /* nCodecDelay */
+    } else if (enc->codec_id == AV_CODEC_ID_MP2) {
+        hdrsize += 22;
+        /* fwHeadLayer */
+        bytestream_put_le16(&riff_extradata, 2);
+        /* dwHeadBitrate */
+        bytestream_put_le32(&riff_extradata, enc->bit_rate);
+        /* fwHeadMode */
+        bytestream_put_le16(&riff_extradata, enc->channels == 2 ? 1 : 8);
+        /* fwHeadModeExt */
+        bytestream_put_le16(&riff_extradata, 0);
+        /* wHeadEmphasis */
+        bytestream_put_le16(&riff_extradata, 1);
+        /* fwHeadFlags */
+        bytestream_put_le16(&riff_extradata, 16);
+        /* dwPTSLow */
+        bytestream_put_le32(&riff_extradata, 0);
+        /* dwPTSHigh */
+        bytestream_put_le32(&riff_extradata, 0);
+    } else if (enc->codec_id == AV_CODEC_ID_GSM_MS ||
+               enc->codec_id == AV_CODEC_ID_ADPCM_IMA_WAV) {
+        hdrsize += 2;
+        /* wSamplesPerBlock */
+        bytestream_put_le16(&riff_extradata, frame_size);
+    } else if (enc->extradata_size) {
+        riff_extradata_start = enc->extradata;
+        riff_extradata       = enc->extradata + enc->extradata_size;
+        hdrsize             += enc->extradata_size;
+    }
+    /* write WAVEFORMATEXTENSIBLE extensions */
+    if (waveformatextensible) {
+        hdrsize += 22;
+        /* 22 is WAVEFORMATEXTENSIBLE size */
+        avio_wl16(pb, riff_extradata - riff_extradata_start + 22);
+        /* ValidBitsPerSample || SamplesPerBlock || Reserved */
+        avio_wl16(pb, bps);
+        /* dwChannelMask */
+        avio_wl32(pb, enc->channel_layout);
+        /* GUID + next 3 */
+        avio_wl32(pb, enc->codec_tag);
+        avio_wl32(pb, 0x00100000);
+        avio_wl32(pb, 0xAA000080);
+        avio_wl32(pb, 0x719B3800);
+    } else {
+        avio_wl16(pb, riff_extradata - riff_extradata_start); /* cbSize */
+    }
+    avio_write(pb, riff_extradata_start, riff_extradata - riff_extradata_start);
+    if (hdrsize & 1) {
+        hdrsize++;
+        avio_w8(pb, 0);
+    }
+
+    return hdrsize;
+}
+
+/* BITMAPINFOHEADER header */
+void ff_put_bmp_header(AVIOContext *pb, AVCodecContext *enc,
+                       const AVCodecTag *tags, int for_asf)
+{
+    /* size */
+    avio_wl32(pb, 40 + enc->extradata_size);
+    avio_wl32(pb, enc->width);
+    //We always store RGB TopDown
+    avio_wl32(pb, enc->codec_tag ? enc->height : -enc->height);
+    /* planes */
+    avio_wl16(pb, 1);
+    /* depth */
+    avio_wl16(pb, enc->bits_per_coded_sample ? enc->bits_per_coded_sample : 24);
+    /* compression type */
+    avio_wl32(pb, enc->codec_tag);
+    avio_wl32(pb, enc->width * enc->height * 3);
+    avio_wl32(pb, 0);
+    avio_wl32(pb, 0);
+    avio_wl32(pb, 0);
+    avio_wl32(pb, 0);
+
+    avio_write(pb, enc->extradata, enc->extradata_size);
+
+    if (!for_asf && enc->extradata_size & 1)
+        avio_w8(pb, 0);
+}
+
+void ff_parse_specific_params(AVCodecContext *stream, int *au_rate,
+                              int *au_ssize, int *au_scale)
+{
+    int gcd;
+    int audio_frame_size;
+
+    /* We use the known constant frame size for the codec if known, otherwise
+     * fall back on using AVCodecContext.frame_size, which is not as reliable
+     * for indicating packet duration. */
+    audio_frame_size = av_get_audio_frame_duration(stream, 0);
+    if (!audio_frame_size)
+        audio_frame_size = stream->frame_size;
+
+    *au_ssize = stream->block_align;
+    if (audio_frame_size && stream->sample_rate) {
+        *au_scale = audio_frame_size;
+        *au_rate  = stream->sample_rate;
+    } else if (stream->codec_type == AVMEDIA_TYPE_VIDEO ||
+               stream->codec_type == AVMEDIA_TYPE_DATA ||
+               stream->codec_type == AVMEDIA_TYPE_SUBTITLE) {
+        *au_scale = stream->time_base.num;
+        *au_rate  = stream->time_base.den;
+    } else {
+        *au_scale = stream->block_align ? stream->block_align * 8 : 8;
+        *au_rate  = stream->bit_rate ? stream->bit_rate :
+                    8 * stream->sample_rate;
+    }
+    gcd        = av_gcd(*au_scale, *au_rate);
+    *au_scale /= gcd;
+    *au_rate  /= gcd;
+}
+
+void ff_riff_write_info_tag(AVIOContext *pb, const char *tag, const char *str)
+{
+    int len = strlen(str);
+    if (len > 0) {
+        len++;
+        ffio_wfourcc(pb, tag);
+        avio_wl32(pb, len);
+        avio_put_str(pb, str);
+        if (len & 1)
+            avio_w8(pb, 0);
+    }
+}
+
+static const char riff_tags[][5] = {
+    "IARL", "IART", "ICMS", "ICMT", "ICOP", "ICRD", "ICRP", "IDIM", "IDPI",
+    "IENG", "IGNR", "IKEY", "ILGT", "ILNG", "IMED", "INAM", "IPLT", "IPRD",
+    "IPRT", "ISBJ", "ISFT", "ISHP", "ISRC", "ISRF", "ITCH",
+    { 0 }
+};
+
+static int riff_has_valid_tags(AVFormatContext *s)
+{
+    int i;
+
+    for (i = 0; *riff_tags[i]; i++)
+        if (av_dict_get(s->metadata, riff_tags[i], NULL, AV_DICT_MATCH_CASE))
+            return 1;
+
+    return 0;
+}
+
+void ff_riff_write_info(AVFormatContext *s)
+{
+    AVIOContext *pb = s->pb;
+    int i;
+    int64_t list_pos;
+    AVDictionaryEntry *t = NULL;
+
+    ff_metadata_conv(&s->metadata, ff_riff_info_conv, NULL);
+
+    /* writing empty LIST is not nice and may cause problems */
+    if (!riff_has_valid_tags(s))
+        return;
+
+    list_pos = ff_start_tag(pb, "LIST");
+    ffio_wfourcc(pb, "INFO");
+    for (i = 0; *riff_tags[i]; i++)
+        if ((t = av_dict_get(s->metadata, riff_tags[i],
+                             NULL, AV_DICT_MATCH_CASE)))
+            ff_riff_write_info_tag(s->pb, t->key, t->value);
+    ff_end_tag(pb, list_pos);
+}