Changes between Version 3 and Version 4 of AACEncodingGuide

Timestamp:

01/12/2013 02:51:13 AM (4 months ago)

Author:

llogan

Comment:

add more encoders

AACEncodingGuide

@@ -3 +3 @@
 [[PageOutline(2-3, Contents)]]
 
-[[http://en.wikipedia.org/wiki/Advanced_Audio_Coding|AAC, Advanced Audio Coding]], is the successor format to MP3, and is defined in MPEG-4 part 3. It is often used within an MP4 container format, for music the .m4a extension is customarily used. The second-most common use is within matroska MKV files (used because it has better support for embedded text-based soft subtitles than MP4). The examples in this guide will use the extensions MP4 and M4A.
+[[http://en.wikipedia.org/wiki/Advanced_Audio_Coding|AAC, Advanced Audio Coding]], is the successor format to MP3, and is defined in MPEG-4 part 3. It is often used within an MP4 container format, for music the .m4a extension is customarily used. The second-most common use is within MKV (Matroska) files because it has better support for embedded text-based soft subtitles than MP4. The examples in this guide will use the extensions MP4 and M4A.
+
+FFmpeg can support four AAC-LC encoders (`aac`, `libfaac`, `libfdk_aac`, `libvo_aacenc`) and two AAC-HC encoders (`libaacplus` and `libfdk_aac`). `libaacplus`, `libfaac`, and `libfdk_aac` are considered "non-free", and are therefore non-redistributable meaning you may have trouble finding a build that supports these. Of course you can resolve this by [[CompilationGuide|compiling ffmpeg]].
+
+----
 
 == libfdk_aac ==#fdk_aac
@@ -63 +67 @@
 }}}
 
-Convert the video with [[x264EncodingGuide#twopass|libx264]], with a target of fitting a 90-minute movie on a 700MB(=5734400kb) CD-ROM, mixing the audio down to two channels (WIndows users should use `NUL` rather than `/dev/null`:
+Convert the video with [[x264EncodingGuide#twopass|libx264]], with a target of fitting a 90-minute movie on a 700MB(=5734400kb) CD-ROM, mixing the audio down to two channels (Windows users should use `NUL` rather than `/dev/null`):
 
 {{{
@@ -77 +81 @@
 Unfortunately, many devices that can play AAC-LC (the default profile for fdk_aac) simply cannot play either version of AAC-HE, so this is not recommended for surround sound audio, which normally needs to be compatible with such hardware players. If you are only going to play it on your computer, or you are sure that your hardware player supports AAC-HE, you can aim for a bit rate of 160kb/s for version 1, or 128kb/s for version 2. As always, experiment to see what works for your ears.
 
-The following examples are taken from [[http://ubuntuforums.org/showpost.php?p=12421935&postcount=34|this ubuntuforum post]].
+The following examples are taken from [[http://ubuntuforums.org/showpost.php?p=12421935&postcount=34|this ubuntuforums post]].
 
 ==== AAC-HE version 1 ====
@@ -91 +95 @@
 }}}
 
-== ffmpeg AAC ==
+----
 
-If your version of ffmpeg isn't built with `--enable-libfdk_aac`, you can use ffmpeg's internal AAC encoder. Note that you will not get as good results as with fdk_aac.
+== Native FFmpeg AAC encoder ==
+
+The native FFmpeg AAC encoder is included with ffmpeg and is does not require an external library like the AAC encoders described here. Note that you will not get as good results as with libfdk_aac. The `-cutoff` option may improve quality according to [http://d.hatena.ne.jp/kamedo2/20120729/1343545890 Quality Assessment of FFmpeg AAC]. This encoder does not currently work with `-q:a`/`-qscale:a` (see ticket #[ticket:1346]).
 
 ==== Example ====
 
 {{{
-ffmpeg -i input.wav -strict experimental -c:a aac -b:a 128k output.m4a
+ffmpeg -i input.wav -strict experimental -c:a aac -cutoff 15000 -b:a 128k output.m4a
 }}}
+
+----
+
+== libvo_aacenc ==
+
+!VisualOn AAC encoding library. Requires ffmpeg configuration with `--enable-libvo-aacenc`. This has the advantage of not being non-free, and is included by some distributors, but is a rather poor encoder compared to libfdk_aac and even the native FFmpeg AAC encoder according to [http://d.hatena.ne.jp/kamedo2/20120729/1343545890 Quality Assessment of FFmpeg AAC].
+
+==== Example ====
+{{{
+ffmpeg -i input.wav -c:a libvo_aacenc -b:a 128k output.m4a
+}}}
+
+----
+
+== libfaac ==
+
+Freeware Advanced Audio Coder. Requires ffmpeg configuration with the ironic options of `--enable-libfaac --enable-nonfree`.
+
+==== VBR Example ====
+{{{
+ffmpeg -i input.wav -c:a libfaac -q:a 100 output.m4a
+}}}
+
+Range for `-q:a` is 0-250 and is similar to using the `-q` option in standalone `faac`.
+
+==== CBR Example ====
+{{{
+ffmpeg -i input.wav -c:a libfaac -b:a 128k output.m4a
+}}}
+
+----
+
+== Metadata ==
+You can add metadata to any of the examples on this guide:
+
+{{{
+ffmpeg -i input ... -metadata author="FFmpeg Bayou Jug Band" -metadata title="Decode my Heart" output.mp4
+}}}
+
+----
+
+== FAQ ==
+=== Which encoder should I use? What provides the best quality? ===
+
+It depends. For AAC-LC the likely answer is: libfdk_aac > libfaac > FFmpeg AAC ≥ libvo_aacenc.
+
+=== Should I use AAC-LC or AAC-HE? ===
+
+It also depends. If you require a low audio bitrate, such as ≤ 32kbs/channel, then AAC-HE would be worth considering depending if your player or device can support AAC-HE decoding. Anything higher may benefit more from AAC-LC due to less processing. If in doubt use AAC-LC.
+
+{{{#!comment
+todo: 
+Find out if libfdk_aac and libaacplus can be installed/supported at the same time. I can't remember. If not then add error(s) and any trac ticket # to FAQ and/or each encoder's section.
+
+List available metadata options for the MP4 container.
+}}}