[FFmpeg-user] Download audio only bytes with ffmpeg

[Feras Salim]

Can you give me any clues on how to do that ? Thanks!


On Fri, Oct 25, 2013 at 10:28 AM, Robert Krüger <krueger at lesspain.de> wrote:

> On Fri, Oct 25, 2013 at 10:48 AM, Tom Evans <tevans.uk at googlemail.com>
> wrote:
> > On Thu, Oct 24, 2013 at 5:42 PM, Feras Salim <feribg at gmail.com> wrote:
> >> Hi,
> >> I noticed a few youtube downloaders out there give the option of
> >> downloading only the audio and skipping the video stream. I was
> wondering
> >> if that is possible with ffmpeg.
> >
> > Yes
> >
> >> Given we have an url that has flv or mp4
> >> source and is seekable, is it possible to download only the audio form
> it
> >> and convert to mp3, without having to download the whole file first.
> >
> > No. Audio and video packets are typically interweaved with each other,
> > to split out the audio you need to demux the entire file. The "youtube
>
> I don't know what the downloader really does but technically it is
> possible at least with a seekable mp4 stream (don't know much about
> flv) to read the positions of only audio sample chunks in the moov
> atom and only download them by seeking to their start position one
> after the other. Don't know how much you would practically gain
> because of the tons of seeks you would have to do.
>
> > downloaders" are also downloading the whole file.
> >
> >> I tried the following commands but all of them resulted in using the
> >> bandwidth to download the entire video:
> >>
> >> ffmpeg -i "url" output.mp3
> >> ffmpeg -i "url" -vn -c:a copy output.mp3
> >> ffmpeg –i video.flv –vn –c:a libaac –ar 44100 –ac 2 –ab 64k audio.mp3
> >> ffmpeg -i video.flv -ab 160k -ac 2 -ar 44100 -vn audio.mp3
> >> ffmpeg -i “input” -vn -acodec copy output.mp3
> >> ffmpeg -i "input" -vn out.mp3
> >>
> >> Is doing something like that even possible?
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