Re: [FFmpeg-devel] [PATCH] avformat/aea: Add aea muxer

[asivery via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

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Great, thank you very much!
I'm attaching the (hopefully) final version of the patch.

MD studio was a piece of software created by a company called "EDL", which in combination with alternative firmware for the Sony MDH-10 MiniDisc recorder (https://www.minidisc.wiki/equipment/sony/misc/mdh-10) let people download raw ATRAC1 audio from their MiniDiscs onto computers, and (probably) put this audio back on their discs later.
Nowadays it's used by software like Web Minidisc Pro (which I maintain) to store ATRAC1 audio, as it (until recently) was the only way to store ATRAC1 so that it would be picked up by VLC. Now we have matroska support for ATRAC1, but I wanted to write a muxer for AEA before I phase it out from new pieces of software, so that the people who would like to use AEA instead of matroska have a way to go back to it.

> On date Saturday 2024-03-09 17:20:49 +0000, ffmpeg-devel Mailing List wrote:
> 
> > Thank you both for the suggestions. I've updated the code as requested, and I apologize for the AV_LOG_WARNING instead of AV_LOG_ERROR - it was an oversight on my part.
> > I have also added the stream codec check, and it did get triggered when I tried to feed it audio that was not ATRAC1, so it seems it is required.
> > Regarding titles being truncated - that was my intention. However I've now added a warning if it was going to happen.
> > As for the block count in the header - none of the modern software which uses AEA reads that field, but for the older software, it will now be truncated to UINT32_MAX if needed.
> > Is there anything else that needs changes?
> 
> > From ee1d4c93c66e729d9d0456b2e8e789f3f98389e3 Mon Sep 17 00:00:00 2001
> > From: asivery asivery@protonmail.com
> > Date: Fri, 8 Mar 2024 14:45:02 +0100
> > Subject: [PATCH] avformat/aea: Add aea muxer
> > 
> > Signed-off-by: asivery asivery@protonmail.com
> > ---
> > doc/muxers.texi | 10 +++
> > libavformat/Makefile | 3 +-
> > libavformat/{aea.c => aeadec.c} | 0
> > libavformat/aeaenc.c | 115 ++++++++++++++++++++++++++++++++
> > libavformat/allformats.c | 1 +
> > 5 files changed, 128 insertions(+), 1 deletion(-)
> > rename libavformat/{aea.c => aeadec.c} (100%)
> > create mode 100644 libavformat/aeaenc.c
> > 
> > diff --git a/doc/muxers.texi b/doc/muxers.texi
> > index 2104cc4a95..a4df8f736d 100644
> > --- a/doc/muxers.texi
> > +++ b/doc/muxers.texi
> > @@ -663,6 +663,16 @@ when enabled, write a CRC checksum for each packet to the output,
> > default is @code{false}
> > @end table
> 
> > +@anchor{aea}
> > +@section aea
> 
> 
> nit: sort order (should go after adts)
> 
> > +MD STUDIO audio muxer.
> 
> 
> out of my own curiosity, what is MD STUDIO?
> 
> [...]
> 
> You might also add an entry to the Changelog.
> Looks good to me otherwise, thanks.

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From e67d2df52c65528fbbfe8d5268661c88a7ad225e Mon Sep 17 00:00:00 2001
From: asivery <asivery@protonmail.com>
Date: Fri, 8 Mar 2024 14:45:02 +0100
Subject: [PATCH] avformat/aea: Add aea muxer

Signed-off-by: asivery <asivery@protonmail.com>
---
 Changelog                       |   1 +
 doc/muxers.texi                 |  10 +++
 libavformat/Makefile            |   3 +-
 libavformat/{aea.c => aeadec.c} |   0
 libavformat/aeaenc.c            | 115 ++++++++++++++++++++++++++++++++
 libavformat/allformats.c        |   1 +
 6 files changed, 129 insertions(+), 1 deletion(-)
 rename libavformat/{aea.c => aeadec.c} (100%)
 create mode 100644 libavformat/aeaenc.c

diff --git a/Changelog b/Changelog
index 069b827448..641c6b7cc5 100644
--- a/Changelog
+++ b/Changelog
@@ -32,6 +32,7 @@ version <next>:
 - DVD-Video demuxer, powered by libdvdnav and libdvdread
 - ffprobe -show_stream_groups option
 - ffprobe (with -export_side_data film_grain) now prints film grain metadata
+- AEA muxer
 
 
 version 6.1:
diff --git a/doc/muxers.texi b/doc/muxers.texi
index 2104cc4a95..6446d868ed 100644
--- a/doc/muxers.texi
+++ b/doc/muxers.texi
@@ -684,6 +684,16 @@ Enable to set MPEG version bit in the ADTS frame header to 1 which
 indicates MPEG-2. Default is 0, which indicates MPEG-4.
 @end table
 
+@anchor{aea}
+@section aea
+MD STUDIO audio muxer.
+
+This muxer accepts a single ATRAC1 audio stream with either one or two channels
+and a sample rate of 44100Hz.
+
+As AEA supports storing the track title, this muxer will also write
+the title from stream's metadata to the container.
+
 @anchor{aiff}
 @section aiff
 Audio Interchange File Format muxer.
diff --git a/libavformat/Makefile b/libavformat/Makefile
index 8811a0ffc9..70d56f391f 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -91,7 +91,8 @@ OBJS-$(CONFIG_ADTS_MUXER)                += adtsenc.o apetag.o img2.o \
                                             id3v2enc.o
 OBJS-$(CONFIG_ADX_DEMUXER)               += adxdec.o
 OBJS-$(CONFIG_ADX_MUXER)                 += rawenc.o
-OBJS-$(CONFIG_AEA_DEMUXER)               += aea.o pcm.o
+OBJS-$(CONFIG_AEA_DEMUXER)               += aeadec.o pcm.o
+OBJS-$(CONFIG_AEA_MUXER)                 += aeaenc.o rawenc.o
 OBJS-$(CONFIG_AFC_DEMUXER)               += afc.o
 OBJS-$(CONFIG_AIFF_DEMUXER)              += aiffdec.o aiff.o pcm.o \
                                             mov_chan.o replaygain.o
diff --git a/libavformat/aea.c b/libavformat/aeadec.c
similarity index 100%
rename from libavformat/aea.c
rename to libavformat/aeadec.c
diff --git a/libavformat/aeaenc.c b/libavformat/aeaenc.c
new file mode 100644
index 0000000000..f7b945b382
--- /dev/null
+++ b/libavformat/aeaenc.c
@@ -0,0 +1,115 @@
+/*
+ * MD STUDIO audio muxer
+ *
+ * Copyright (c) 2024 asivery
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "avformat.h"
+#include "avio_internal.h"
+#include "rawenc.h"
+#include "mux.h"
+
+static int aea_write_header(AVFormatContext *s)
+{
+    const AVDictionaryEntry *title_entry;
+    size_t title_length = 0;
+    AVStream *st;
+
+    if (s->nb_streams > 1) {
+        av_log(s, AV_LOG_ERROR, "Got more than one stream to encode. This is not supported.\n");
+        return AVERROR(EINVAL);
+    }
+    
+    st = s->streams[0];
+    if (st->codecpar->ch_layout.nb_channels != 1 && st->codecpar->ch_layout.nb_channels != 2) {
+        av_log(s, AV_LOG_ERROR, "Only maximum 2 channels are supported in the audio"
+               " stream, %d channels were found.\n", st->codecpar->ch_layout.nb_channels);
+        return AVERROR(EINVAL);
+    }
+
+    if (st->codecpar->codec_id != AV_CODEC_ID_ATRAC1) {
+        av_log(s, AV_LOG_ERROR, "AEA can only store ATRAC1 streams, %s was found.\n", avcodec_get_name(st->codecpar->codec_id));
+        return AVERROR(EINVAL);
+    }
+
+    if (st->codecpar->sample_rate != 44100) {
+        av_log(s, AV_LOG_ERROR, "Invalid sample rate (%d) AEA only supports 44.1kHz.\n", st->codecpar->sample_rate);
+        return AVERROR(EINVAL);
+    }
+
+    /* Write magic */
+    avio_wl32(s->pb, 2048);
+    
+    /* Write AEA title */
+    title_entry = av_dict_get(st->metadata, "title", NULL, 0);
+    if (title_entry) {
+        const char *title_contents = title_entry->value;
+        title_length = strlen(title_contents);
+        if (title_length > 256) {
+            av_log(s, AV_LOG_WARNING, "Title too long, truncated to 256 bytes.\n");
+            title_length = 256;
+        }
+        avio_write(s->pb, title_contents, title_length);
+    }
+
+    ffio_fill(s->pb, 0, 256 - title_length);
+
+    /* Write number of frames (zero at header-writing time, will seek later), number of channels */
+    avio_wl32(s->pb, 0);
+    avio_w8(s->pb, st->codecpar->ch_layout.nb_channels);
+    avio_w8(s->pb, 0);
+
+    /* Pad the header to 2048 bytes */
+    ffio_fill(s->pb, 0, 1782);
+
+    return 0;
+}
+
+static int aea_write_trailer(struct AVFormatContext *s)
+{
+    int64_t total_blocks;
+    AVIOContext *pb = s->pb;
+    AVStream *st = s->streams[0];
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
+        /* Seek to rewrite the block count. */
+        avio_seek(pb, 260, SEEK_SET);
+        total_blocks = st->nb_frames * st->codecpar->ch_layout.nb_channels;
+        if (total_blocks > UINT32_MAX) {
+            av_log(s, AV_LOG_WARNING, "Too many frames in the file to properly encode the header (%ld)."
+                   " Block count in the header will be truncated.\n", total_blocks);
+            total_blocks = UINT32_MAX;
+        }
+        avio_wl32(pb, total_blocks);
+    } else {
+        av_log(s, AV_LOG_WARNING, "Unable to rewrite AEA header.\n");
+    }
+
+    return 0;
+}
+
+const FFOutputFormat ff_aea_muxer = {
+    .p.name           = "aea",
+    .p.long_name      = NULL_IF_CONFIG_SMALL("MD STUDIO audio"),
+    .p.extensions     = "aea",
+    .p.audio_codec    = AV_CODEC_ID_ATRAC1,
+
+    .write_header     = aea_write_header,
+    .write_packet     = ff_raw_write_packet,
+    .write_trailer    = aea_write_trailer,
+};
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index 0a0e76138f..5639715104 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -47,6 +47,7 @@ extern const FFOutputFormat ff_adts_muxer;
 extern const FFInputFormat  ff_adx_demuxer;
 extern const FFOutputFormat ff_adx_muxer;
 extern const FFInputFormat  ff_aea_demuxer;
+extern const FFOutputFormat ff_aea_muxer;
 extern const FFInputFormat  ff_afc_demuxer;
 extern const FFInputFormat  ff_aiff_demuxer;
 extern const FFOutputFormat ff_aiff_muxer;
-- 
2.34.1


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