Re: [ecasound] extract, mix and save questions

Jeremy Hall wrote:

>Hi Brad,
>
>I think you could do this with ecasound
>
>When I want to know how long a file is, I have a variety of ways to do it:
>
>1: if the file is a .wav file strip off the first 44 bytes (NOTE there may
>be length information in the header but often times there isn't, so best
>to calculate it manually)
>
>Let us assume your file is 16-bit samples and 2 channels--you can have
>more channels)
>
>(len - 44) / 4
>
>This is assuming 8 bits to a byte, two channels, two bytes (16-bit) now
>you have the number of "frames"
>
>Now divide that by your srate--this will tell you (hopefully with
>milisecond accuracy) how many seconds the file is. Alternatively, load
>your file into ecasound, connect the chain and issue the fs command from
>interactive mode--this will tell you with ms accuracy as well.
>
>Now for your second task, locate the second file and do:
>
>ecasound -i foo.raw -y:1800 -t:30 -o foo2.raw
>
>This is the second file, -y means offset into the file, -t says how long
>it should run.
>
>
thanks, jeremy.
At this point, foo2.raw is the extracted file that is 30seconds long,
right? I assume that you are saying that the file in step1 is 30sec long.

BTW, Do you know if there is a way to have it start at the closest zero
crossing?

>Next mix them down
>
>ecasound -a:1 -i source1.wav -y:1500 -a:2 -i foo2.wav -a:1,2 -o foo3.wav
>
>
I don't know why you used -y here. foo2.wav should be the length of the
first file (source1.wav). I guess the issue is how does ecasound mix the
two? does it bypass the WAV header and start at index 0 in the audio
data (I assume that it does). If that's the case, then wouldn't it be:

ecasound -a:1 -i source1.wav -a:2 -i foo2.wav -a:1,2 -o foo3.wav

Where source1.wav is the file in the first step: source1.wav and
foo2.wav should be the exact same length.
(also assuming there is a step before this that converts foo2.raw to
foo2.wav)

>It is important to make sure you use the same srate and that you read
>through the requirements from going from mono to stereo etc--use the erc
>effect if you want mono in stereo mode.
>
>Is that what you want? NOTE ecasound does an implicit -ea:50 on each chain
>(because there are two, and 50+50 == 100) so you may need to adjust your
>coefficients during mixing.
>
>
That's good to know, and it's appropriate that it does that.

>Hope this helps.
>
>_J
>
>In the new year, Brad Fuller wrote:
>
>
>>I couldn't find a way to do this in ecasound, but maybe there's a way to
>>do it. Here's what I want to do:
>>
>>Find the exact length of a audio file in ms. I think ecalength can do
>>this, I know it's not sample accurate, but I just need down to the
>>around 1ms. Maybe there's another option other than ecalength. I´d like
>>to have it sample accurate, or at least to the nearest zero crossings.
>>
>>Then, I want to extract a section of another file: at a specific
>>location in ms and at a length of the file above. I see that sox may be
>>able to do this using the 'trim" feature.
>>
>>Then, mix that extracted segment with another file and save the result
>>to a new file.
>>
>>How can this be done? Any ideas?
>>
>>thanks,
>>
>>brad
>>
>>
>>

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Received on Tue Dec 20 00:15:09 2005