[FFmpeg-user] (no subject)

[bouke]

----- Original Message ----- 
From: "Andy Andy" <x2305andy2305x at yahoo.com>
To: <ffmpeg-user at ffmpeg.org>
Sent: Tuesday, August 09, 2011 12:35 PM
Subject: [FFmpeg-user] (no subject)


> Hi guys,
>
> I have a simple uncompressed WAV file, which i want to split. The problem 
> is that i amost never get the precise exact amount of sound i want, as per 
> example:
>
> ffmpeg -i 17203588.wav -ss 1 -t 1 17203588_cut.wav
>
> should cut out exactly one second from the stream, but:
>
> ffmpeg -i 17203588_cut.wav
>
> outputs:
> ffmpeg version N-31743-g324b8ad, Copyright (c) 2000-2011 the FFmpeg 
> developers
> built on Aug 3 2011 15:13:54 with gcc 4.5.2
> .....
> Input #0, wav, from 
> '/home/alexandru-david/Exporter/exportWAV/userclips/17203588_cut.wav':
> Duration: 00:00:00.99, bitrate: 1411 kb/s
> Stream #0.0: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
> At least one output file must be specified
>
>
> This is a pretty happy case though, sometimes i'm missing more millis from 
> the output. And it's very important to get the precise length i need 
> because i'm concatting those WAVs and sometimes i get little pauses at 
> concat time in the final sound.
>
> Any ideas, tips or tricks for me?


Not sure why FFmpeg would not work, but if you can simply copy bytes into a 
new file,  and change a few bytes here and there, you can go sample 
accurate.
Wave is a pretty simple format, see here:
https://ccrma.stanford.edu/courses/422/projects/WaveFormat/

So, copy the header, dive into the datastream and append as much as you 
need, then modify size according to the amount of bytes copied.
If you really want to do it well, look around your desired cut point to see 
if you can find low volume values, or at least close to equal values with 
the previous/next clip, to avoid pops in the output.

Or, have a look at SOX...

hth,
Bouke


> Thanks in advance,
>
> Regards,
> DAV
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