Esoterica alert: This message is only relevant for users who create
their own builds of FFmpeg for use with get_iplayer. If you use the
Windows installer, or a pre-built version of FFmpeg on any platform,
avoid potentially dangerous eye-glazing and hit delete now.
The ever-vigilant Bat Guano has alerted me to a recent change in the git
HEAD version of FFmpeg that will affect anyone doing their own builds
for use with get_iplayer. This is probably most relevant to Linux
users, but would apply on all platforms.
Current Status: get_iplayer internally uses "-absf aac_adtstoasc" in an
FFmpeg command line in order to strip out ADTS frame headers when
creating a M4A file from AAC audio. This is done primarily for the
benefit of iTunes, Winamp, WMP, and other media players that otherwise
couldn't play the AAC audio in the downloaded FLV file or the
intermediate AAC file created by get_iplayer+FFmpeg. VLC, Banshee,
Totem, etc., can usually play the FLV and AAC files without problem.
What Changed: A commit to the main FFmpeg repository
(http://git.videolan.org/?p=ffmpeg.git) on 5 Sep replaced the
-{a,v,s}bsf command line options (for audio, video, subtitle bitstream
filters) with a single -bsf option (for all types of bitstream filters
in a comma-separated list), and removed the old options. So, if you
build FFmpeg from HEAD using code pulled on or after 5 Sep, it will
choke on the old command-line option used by get_iplayer. This only
applies to flashaac-mode radio programmes, of course.
While it wouldn't be difficult to add new options to get_iplayer to
compensate for this (anybody who wants to, please feel free), but it
might be a good idea to wait a bit to see if the FFmpeg developers make
any nod towards backwards compatibility. Señor Guano has queried the
FFmpeg list on the matter.
In the meantime, some other possibilities:
1. If you really need a post-5 Sep HEAD build of FFmpeg for some reason,
and you're not picky about formats, use --aactomp3 to create MP3 files
instead of M4A. If you're not bothered about having tagged files, you
can just use --raw and play the downloaded FLV file with VLC or similar.
[h/t Bat Guano]
2. You may not need to build your own FFmpeg at all. If your software
repositories offer any version of FFmpeg from the 0.7 or 0.8 lines, that
should work. Even some 0.6 versions will work if they were merged with
later code before 0.7 was released.
3. Build FFmpeg from the 0.8 line. There are various recipes around for
building FFmpeg from a clone of its git repository, such as these for
Ubuntu:
http://ubuntuforums.org/showthread.php?t=786095
The only additional step necessary for a get_iplayer-compatible build is
to check out code from the 0.8 line before configure and build. The
basic steps would look like:
Clone the FFmpeg repo:
$ git clone git://git.videolan.org/ffmpeg
Go to cloned repo:
$ cd ffmpeg
Checkout the latest tag from the 0.8 line:
$ git checkout n0.8.3
n0.8.3 is the latest as of this writing. You'll see a warning about
being in detached head state since you're checking out a tag
Instead of checking out a tag, you could create a remote tracking branch
to build the very latest revision in the 0.8 line:
$ git checkout release/0.8
To keep things simple, I'd suggest sticking with a known tag.
Now configure, make, install, etc., as usual.
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