BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Normalize WAV file? Goto page 1, 2  Next          BorlandTalk.com Forum Index -> Delphi Multimedia View previous topic :: View next topic   Author Message Dave Atkin Guest Posted: Thu Aug 10, 2006 8:11 am    Post subject: Normalize WAV file? Hi all, Is there an easy way to normalize a wav file using Delphi. In theory I know that I need to scan the data chunk of the file and look for the loudest sample, calculate how much louder that sample could go without clipping, and then bring up the volume of all the samples by that amount. In practise I have no idea how to do it! I'm a newbie when it comes to working with wav files, so any pointers will be gratefully received! Best regards, Dave Atkin Back to top Boian Mitov Guest Posted: Thu Aug 10, 2006 8:11 am    Post subject: Re: Normalize WAV file? Hi Dave, You can use the Win32 API : var Rtn : Integer; AudioInfo : TAVIStreamInfo; .... .... Rtn := AVIFileOpen(@FAVIFile, @(FFileName[1]), 0, nil); if ( Rtn <> 0) then Exit; // Get Audio Info. AVIFileGetStream(FAVIFile, @FAudioStream, streamtypeAUDIO, 0); if( FAudioStream = NIL ) then begin AVIFileRelease(FAVIFile); Exit; end; AVIStreamInfo(FAudioStream, @AudioInfo, sizeof(AudioInfo)); .... .... // In a loop: if( AVIStreamRead( FAudioStream, FReadPosition, Size, PData, ABufferLength, @ABufferLength, @ALengthRead ) <> 0 ) then begin Result := -1; Exit; end; .... .... if( FAudioStream <> NIL )then AVIStreamRelease(FAudioStream); if( FAVIFile <> NIL ) then AVIFileRelease(FAVIFile); FAudioStream := nil; You can also use AudioLab - www.mitov.com which is free for personal usage. The code snippets are from parts of the library . With best regards, Boian Mitov Dave Atkin wrote: Quote: Hi all, Is there an easy way to normalize a wav file using Delphi. In theory I know that I need to scan the data chunk of the file and look for the loudest sample, calculate how much louder that sample could go without clipping, and then bring up the volume of all the samples by that amount. In practise I have no idea how to do it! I'm a newbie when it comes to working with wav files, so any pointers will be gratefully received! Back to top Dave Atkin Guest Posted: Fri Aug 11, 2006 4:30 am    Post subject: Re: Normalize WAV file? Hi Boian, Thanks for the info. Quote: Rtn := AVIFileOpen(@FAVIFile, @(FFileName[1]), 0, nil); if ( Rtn <> 0) then Exit; // Get Audio Info. AVIFileGetStream(FAVIFile, @FAudioStream, streamtypeAUDIO, 0); if( FAudioStream = NIL ) then begin AVIFileRelease(FAVIFile); Exit; end; AVIStreamInfo(FAudioStream, @AudioInfo, sizeof(AudioInfo)); etc... I notice the code refers to AVI Files - I'm working with WAV Files, does this make a difference? Best regards, Dave Atkin Back to top Boian Mitov Guest Posted: Fri Aug 11, 2006 10:00 pm    Post subject: Re: Normalize WAV file? Hi Dave, It will work . With best regards, Boian Mitov Dave Atkin wrote: Quote: I notice the code refers to AVI Files - I'm working with WAV Files, does this make a difference? Back to top Dave Atkin Guest Posted: Sat Aug 12, 2006 6:16 am    Post subject: Re: Normalize WAV file? Hi Boian, Thanks again, but could you explain which part of the code does the volume checking, and which part does the actual normalization - I'm finding it hard to follow and I need to understand how the process works. My knowledge is very limited in this area :) Best regards, Dave Atkin. Back to top Boian Mitov Guest Posted: Sat Aug 12, 2006 8:11 am    Post subject: Re: Normalize WAV file? Hi Dave, Actually, I just sent you the code that will read the WAVE data into your own buffer. The normalization is up to you from that point . With best regards, Boian Mitov Dave Atkin wrote: Quote: Thanks again, but could you explain which part of the code does the volume checking, and which part does the actual normalization - I'm finding it hard to follow and I need to understand how the process works. Back to top Dave Atkin Guest Posted: Mon Aug 14, 2006 2:30 am    Post subject: Re: Normalize WAV file? Hi Boian & all, My original post was a question about "normalizing a WAV file", not about reading one into a buffer, which I already know how to do! Boian Mitov has kindly showed me another way to read the wave data into a buffer, but I still need some pointers as to how to calculate the loudest sample, and how to subsequently normalize the data - which is what I asked in my original post. If anyone is able to help here I would be extremely grateful :) Best regards, Dave Atkin Back to top Boian Mitov Guest Posted: Mon Aug 14, 2006 2:57 am    Post subject: Re: Normalize WAV file? Hi Dave, I am sorry, I misunderstood the question. Knowing the Wave format, you can move from sample to sample. The nBlockAlign field of the format will give you the step. If the data is 8 bit (wBitsPerSample = , each sample fits in a character, if wBitsPerSample = 16 - ShortInt, nChannels gives you the number of channels. The procedure is simple. You go from sample to sample and you compare the absolute value with the saved MaxValue to thi point. If the sample value is bigger than MaxValue, you set MaxValue := SampleValue. When you are done, you have the MaxValue, and then you do a second pass to normalize. With best regards, Boian Mitov Dave Atkin wrote: Quote: Hi Boian & all, My original post was a question about "normalizing a WAV file", not about reading one into a buffer, which I already know how to do! Boian Mitov has kindly showed me another way to read the wave data into a buffer, but I still need some pointers as to how to calculate the loudest sample, and how to subsequently normalize the data - which is what I asked in my original post. If anyone is able to help here I would be extremely grateful Back to top Boian Mitov Guest Posted: Mon Aug 14, 2006 3:54 am    Post subject: Re: Normalize WAV file? BTW: The normalization coefficient is: K := Range / MaxValue; where: Range := ( 1 shl wBitsPerSample ) / 2; Boian Mitov wrote: > I am sorry, I misunderstood the question. Back to top Dave Atkin Guest Posted: Mon Aug 14, 2006 6:31 am    Post subject: Re: Normalize WAV file? Hi Boian, Quote: Knowing the Wave format, you can move from sample to sample. The nBlockAlign field of the format will give you the step. If the data is 8 bit (wBitsPerSample = , each sample fits in a character, if wBitsPerSample = 16 - ShortInt, nChannels gives you the number of channels. The procedure is simple. You go from sample to sample and you compare the absolute value with the saved MaxValue to thi point. If the sample value is bigger than MaxValue, you set MaxValue := SampleValue. When you are done, you have the MaxValue, and then you do a second pass to normalize. BTW: The normalization coefficient is: K := Range / MaxValue; where: Range := ( 1 shl wBitsPerSample ) / 2; Thanks for your explanation, I understand much better now :) I am only working with 16 bit samples, so obviously the value can be represented by a ShortInt, but just out of interest - how do you represent the value of a 24 bit sample? Do you need to declare a record containing a Byte & a ShortInt as separate fields, or would you use an array[0..2] of Byte? Just interested for future reference... Best regards, Dave Atkin Back to top Boian Mitov Guest Posted: Mon Aug 14, 2006 6:38 am    Post subject: Re: Normalize WAV file? Hi Dave, Well... This is a different ball game . We are just adding the 24 bit support in our libraries, and it is a bit of challenge. First not all the API supports 24 bits. Second, the description structure is expanded, so all the code has to be changed to accommodate the new bigger structure, finally the data is packed, so each sample is not word aligned. The result is a fair number of shifts and OR operation. Hopefully, we are using IPP functions to optimize the speed . With best regards, Boian Mitov Dave Atkin wrote: Quote: Hi Boian, Thanks for your explanation, I understand much better now :) I am only working with 16 bit samples, so obviously the value can be represented by a ShortInt, but just out of interest - how do you represent the value of a 24 bit sample? Do you need to declare a record containing a Byte & a ShortInt as separate fields, or would you use an array[0..2] of Byte? Just interested for future reference... Back to top Atmapuri Guest Posted: Wed Aug 16, 2006 1:10 pm    Post subject: Re: Normalize WAV file? Hi! Quote: Is there an easy way to normalize a wav file using Delphi. In theory I know that I need to scan the data chunk of the file and look for the loudest sample, calculate how much louder that sample could go without clipping, and then bring up the volume of all the samples by that amount. In practise I have no idea how to do it! I'm a newbie when it comes to working with wav files, so any pointers will be gratefully received! Normalization means that you ensure that the mean value of the wav is zero. This can be achieved with a highpass filter or simply by computing mean of entire wav file and then subtracting it. Normalization is also reffered to when storing floating point wav files. You search for the abs max and divide by it so that the maximum comes between -1 and +1. Once you read the file you determine the bit resolution of A/D and scale it up. You can read 24 bit wav files with our library and also apply a highpass filter. The library is free for educational purposes. www.dewresearch.com Regards! Atmapuri Back to top Dave Atkin Guest Posted: Thu Aug 17, 2006 7:03 am    Post subject: Re: Normalize WAV file? Hi Atmapuri Quote: Normalization means that you ensure that the mean value of the wav is zero This sounds more like DC offset correction... Quote: This can be achieved with a highpass filter How does that work? A high pass filter will attenuate the frequencies below the cutoff point, and pass only the frequencies above that point unattenuated. Im talking about modifying the wav data so that it plays back at it's maximum loudness, as in your second paragraph: Quote: Normalization is also reffered to when storing floating point wav files. You search for the abs max It's confusing when a word has more than one meaning... :) Best regards, Dave Atkin Back to top Staiger Guest Posted: Thu Aug 17, 2006 8:11 am    Post subject: Re: Normalize WAV file? Quote: Normalization means that you ensure that the mean value of the wav is zero This sounds more like DC offset correction... I agree - normalisation "normally" means to adjust the amplitude of the sound so it plays at maximum volume. In other words, to amplify it so that the highest value reaches +/- 32K. (Maximum "loudness", by the way, is usually taken to mean the subjective experience, and frequently involves non-linear companding, such that the quiet passages are amplified more than the loud passages). Atmapuri was talking about DC offset correction. Quote: This can be achieved with a highpass filter How does that work? A high pass filter will attenuate the frequencies below the cutoff point..... You've just said it. A DC offset has an infinitely low frequency, so it will be attenuated to zero by applying a high pass filter. Staiger Back to top Atmapuri Guest Posted: Thu Aug 17, 2006 8:11 am    Post subject: Re: Normalize WAV file? "Dave Atkin" <musictronics (AT) optusnet (DOT) com.au> wrote in message news:44e3ce19 (AT) newsgroups (DOT) borland.com... Quote: Hi Atmapuri Normalization means that you ensure that the mean value of the wav is zero This sounds more like DC offset correction... The formula for normalization is: (X[i] - d)*c d in this case can be mean and c is the scale factor to amplify. I believe there was CoolEdit or a similar program that was doing normalization like that. Of course, you can have d set to zero or c set to 1. Quote: This can be achieved with a highpass filter How does that work? A high pass filter will attenuate the frequencies below the cutoff point, and pass only the frequencies above that point unattenuated. Yes. If your cutoff point is 0Hz, it will remove the DC (the mean). You should not amplify the signal unless its mean is zero, because it will also increase its DC. Regards! 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