[FFmpeg-devel] [PATCH] aacdec: add support for dual mono in Japanese DTV

Michael Niedermayer michaelni at gmx.at
Wed Aug 22 01:24:55 CEST 2012

On Tue, Aug 21, 2012 at 12:54:54AM +0900, atsukada at users.sourceforge.net wrote:
> From: Akihiro Tsukada <atsukada at users.sourceforge.net>
> Japanese DTV uses some non standard extensions in AAC audio.
> One example is 'dual mono', which combines two independent
> audio into one stereo stream, storing them in left and right channels
> respectively.  Historically, dual mono audio has been used for
> multi-lingual audio, one for local/native language, and another for english,
> and usually the "main" (local language) channel should be output without
> any user interactions.
> The frames of those dual mono audio are allowed to set
> ADTS channel_config field to 0, and just contain two SCE's *WITHOUT* PCE,
> which is a non standard extension by Japanese DTV standard.
> (ref. ARIB STD-B32 PartII 5.2.3)
> With this patch, the decoder detects dual mono and
> outputs only the selected channel of user's choice,
> replicating it to the other channel.
> Users can change the output channel by setting AVOption "dual_mono_mode".

> AVOption "jp_dtv_mode" is introduced as well,
> which enables Japanese DTV specific extensions.
> Without this option, fate fails at al17_44.mp4,
> as it also has the configuration of two SCE's.

so there is no way to distinguish dual mono from stereo and the user
has to set this for each program she wants to watch manually ?

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Why not whip the teacher when the pupil misbehaves? -- Diogenes of Sinope
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