[FFmpeg-devel] [PATCH 2/3] doc/encoders: add doc for AAC encoder

[Stefano Sabatini]

On date Sunday 2013-09-08 17:02:05 -0700, Timothy Gu encoded:
> Thanks-to: Kostya Shishkov <kostya.shishkov at gmail.com>
> Signed-off-by: Timothy Gu <timothygu99 at gmail.com>
> ---
>  doc/encoders.texi | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 91 insertions(+)
> 
> diff --git a/doc/encoders.texi b/doc/encoders.texi
> index f85e9c6..3ef8f6b 100644
> --- a/doc/encoders.texi
> +++ b/doc/encoders.texi
> @@ -25,6 +25,96 @@ enabled encoders.
>  A description of some of the currently available audio encoders
>  follows.
>  
> + at anchor{aacenc}
> + at section aac
> +
> +Advanced Audio Coding (AAC) encoder.
> +
> +This encoder is an experimental FFmpeg-native AAC encoder. Currently only the
> +low complexity (AAC-LC) profile is supported. To use this encoder, you must set
> + at option{strict} option to @samp{experimental} or lower.
> +

> +We have done our best to keep this encoder bug-free; however, as this encoder

Just my opinion, remove the first sentence since it's too generic.

> +is experimental, unexpected behavior may exist from time to time. For a more
> +stable AAC encoder, see @ref{libvo-aacenc}. However, be warned that it has a
> +worse quality reported by some users.
> +

> + at c Comment this out until somebody writes the respective documentation.
> + at c See also @ref{libfaac}, @ref{libaacplus}, and @ref{libfdk-aac-enc}.
> +
> + at subsection Options
> +
> + at table @option
> + at item b
> +Set bit rate in bits/s. Setting this automatically activates constant bit rate
> +(CBR) mode.
> +
> + at item q
> +Set quality for variable bit rate (VBR) mode. This option is valid only using
> +the @command{ffmpeg} command-line tool. For library interface users, use
> + at option{global_quality}.
> +

> + at item stereo_mode
> +Set stereo encoding mode. Possible values:
> +
> + at table @samp
> + at item auto
> +Automatically selected by the encoder.
> +
> + at item ms_off
> +Disable middle/side encoding.
> +
> + at item ms_force
> +Force middle/side encoding.
> + at end table

Which is the default value?

> +
> + at item aac_coder
> +Set AAC encoder coding method. Possible values:
> +
> + at table @samp
> + at item faac
> +FAAC-inspired method.
> +
> +This method is a simplified reimplementation of the method used in FAAC, which
> +sets thresholds proportional to the band energies, and then decreases all the
> +thresholds with quantizer steps to find the appropriate quantization with
> +distortion below threshold band by band.
> +
> +The quality of this method is comparable to the two loop searching method
> +descibed below, but somewhat a little better and slower.
> +
> + at item anmr
> +Average noise to mask ratio (ANMR) trellis-based solution.
> +
> +This has a theoretic best quality out of all the coding methods, but at the
> +cost of the slowest speed.
> +
> + at item twoloop
> +Two loop searching (TLS) method.
> +
> +This method first sets quantizers depending on band thresholds and then tries
> +to find an optimal combination by adding or subtracting a specific value from
> +all quantizers and adjusting some individual quantizer a little.
> +
> +This method produces similar quality with the FAAC method and is the default.
> +
> + at item fast
> +Constant quantizer method.
> +
> +This method sets a constant quantizer for all bands. This is the fastest of all
> +the methods, yet produces the worst quality.
> +
> + at end table
> +
> + at end table
> +
> + at subsection Tips and Tricks
> +
> +According to some reports
> +(e.g. @url{http://d.hatena.ne.jp/kamedo2/20120729/1343545890}), setting the
> + at option{cutoff} option to 15000 Hz greatly improves the quality of the output
> +quality. As a result, we encourage you to do the same.
> +
>  @section ac3 and ac3_fixed
>  
>  AC-3 audio encoders.
> @@ -553,6 +643,7 @@ Set MPEG audio original flag when set to 1. The default value is 0
>  
>  @end table
>  
> + at anchor{libvo-aacenc}
>  @section libvo-aacenc

LGTM otherwise, thanks.
-- 
FFmpeg = Furious and Frenzy Mystic Portable EnGine