[FFmpeg-devel] [PATCH] doc/filters/apad: extend documentation

Timothy Gu timothygu99 at gmail.com
Mon Aug 18 18:25:10 CEST 2014


On Mon, Aug 18, 2014 at 5:53 AM, Stefano Sabatini <stefasab at gmail.com> wrote:
> ---
>  doc/filters.texi | 47 +++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 45 insertions(+), 2 deletions(-)
>
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 0ca1d6f..44eecca 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -742,8 +742,51 @@ Pass the audio source unchanged to the output.
>
>  @section apad
>
> -Pad the end of a audio stream with silence, this can be used together with
> --shortest to extend audio streams to the same length as the video stream.
> +Pad the end of an audio stream with silence.
> +
> +This can be used together with @command{ffmpeg} @option{-shortest} to
> +extend audio streams to the same length as the video stream.
> +

> +A description of the accepted parameters follows.

@subsection Options

I would also change "parameters" to "options", as it is more common in the doc.

> +
> + at table @option
> + at item packet_size
> +Set silence packet size. Default value is 4096.
> +

> + at item pad_len
> +Set the number of samples of silence to add to the end. After the
> +value is reached, the stream is terminated. This option is mutually
> +exclusive with @option{whole_len}.
> +
> + at item whole_len

> +Set the target number of sample in the audio stream. After the value
> +is reached, the stream is terminated. This option is mutually
> +exclusive with @option{pad_len}.

How about:

Set total number of samples in the audio stream. If the value is
longer than input audio length, silence is added to the end, until the
value is reached. If it is shorter, the stream is terminated after the
value is reached. This option is mutually exclusive with
@option{pad_len}.

What happens when neither of these are specified (like in your third example)?

> + at end table
> +
> + at subsection Examples
> +
> + at itemize
> + at item
> +Add 1024 samples of silence to the end of the input:
> + at example
> +apad=pad_len=1024
> + at end example
> +
> + at item
> +Make sure the audio output will contain at least 10000 samples, pad
> +the input with silence if required:
> + at example
> +apad=whole_len=10000
> + at end example
> +
> + at item
> +Use @command{ffmpeg} to pad the audio input with silence, so that the
> +video stream will be converted in the output until the end:
> + at example
> +ffmpeg -i VIDEO -i AUDIO -filter_complex "[1:0]apad" -shortest OUTPUT
> + at end example
> + at end itemize
>
>  @section aphaser
>  Add a phasing effect to the input audio.
> --
> 1.8.3.2
>
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