[FFmpeg-devel] [PATCHv2 1/2] ffplay: add support for interactive volume control

[Marton Balint]

On Sun, 27 Sep 2015, Clément Bœsch wrote:

> On Sun, Sep 27, 2015 at 11:57:41AM -0400, Ganesh Ajjanagadde wrote:
>> On Sun, Sep 27, 2015 at 11:40 AM, Clément Bœsch <u at pkh.me> wrote:
>>> On Sun, Sep 27, 2015 at 10:12:52AM -0400, Ganesh Ajjanagadde wrote:
>>> [...]
>>>> Yes, I consider the current usage terrible unless I am missing
>>>> something. volume filter is static, so once set, I can't adjust the
>>>> volume until I reinsert a new volume filter, etc. I can't simply
>>>> adjust the volume like I can with vlc/mpv with a simple keybinding.
>>>>
>>>
>>> There is a process_command() mechanism too if you want to change settings
>>> on the fly
>>
>> Hmm... that seems to be a libavfilter thing. We could consider adding
>> that to the volume filter.
>
> volume filter already supports it (see avfilter_process_command() and
> process_command callback in the filter code)
>

FFplay pre-calculates up to 9 frames in the audio decoder thread, so using 
a filter for volume control would add (a codec-specific) latency. Not 
impossible to find compromise between latency and using a filter for 
control, but it requires a bit of further tuning and/or changes.

Regards,
Marton