From Newsgroup: alt.os.linux.mint
On Tue, 5/12/2026 11:17 AM, Mike Scott wrote:
I've just tried to run dvd-slideshow, having used it quite a few years ago, and found it didn't work this time round.
It tries to run ffmpeg with a "-vol 100" option, but ffmpeg doesn't seem to recognize -vol.
The manpage (nor 'ffmpeg -h full') doesn't list the option, but online ffmpeg docs (github) do.
I've stripped out the -vol stuff from dvd-slideshow (it's only a bash script) and all now seems well.
But what about ffmpeg? should -vol be legit?
FFMPEG consists of several executables. These have similar sizes,
so a lot of the same baseline functions are likely in there. But of necessity, the command line level is different (a player needs player-like parameters).
ffmpeg
ffplay
ffprobe
When you download a package, there is a documentation folder.
This should resemble what is on the ffmpeg.org site.
*******
I've selectively snipped this, just leaving some "highlights".
There is a volume in here.
FFMPEG-doc/ffplay-all.html
3.4 Main options# TOC
-x width
Force displayed width.
-y height
Force displayed height.
-an
Disable audio.
-vn
Disable video.
-sn
Disable subtitles.
-ss pos
Seek to pos. Note that in most formats it is not possible to seek exactly, so ffplay will seek to the nearest seek point to pos.
pos must be a time duration specification, see (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual.
-volume
Set the startup volume. 0 means silence, 100 means no volume reduction or amplification.
Negative values are treated as 0, values above 100 are treated as 100.
*******
Plenty of volume parameters in here, but they're part of format conversions. I'll look through Main Options on this one.
FFMPEG-doc/ffmpeg-all.html#Main-options
5.4 Main options
I don't think there is a volume in that section.
As we'd want a volume on the "outside" of the thing,
any volume setting for an "effect" such as Normalize,
is unlikely to "appear on a screen".
Make sure first of all, that ffplay is being used,
as it's a player, and it must have something for this purpose.
A few applications, use ffmpeg as a "helper" application,
and the main purpose of this is as a stream mux or demux.
For example, yt-dlp will glue together a video stream and
a vaguely related audio stream, to make a movie format on
output, so that might be "muxing and a conversion to fit
the declared container type". Containers are limited on the
CODECs that can be used inside them, which is why a stream
may need format conversion before a final movie is made.
Paul
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