Adobe Audition Nags

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Adobe Audition Nags

2007-02-09 07:04:16

Ok. Dunno if this is just a nuance of my system doing this, but I notice when dealing with editing low resolution audio in Adobe Audition like say 8khz, 8-bit, mono (if you must ask, it's the required format in PCM wav for my motorola iDEN phone to use as ringtones.). When playing back inside audition, it throws in some obviously fake high end frequencies whereas playing back in a different player like mplayer2 or winamp or even on the cellphone itself, it sounds like it should with just that limited audio resolution.

Anyone ever run into this before at all? If so, any way to get rid of this annoyance? Kinda makes it hard to do proper editing when it's not playing back the untouched waveform like it should.

Adobe Audition Nags

Reply #1 – 2007-02-09 19:00:54

Oh. I also did some more testing and two different sound cards produced the same results here. And even playing back standard 44khz audio produced the same effect. I have an mp3 sitting here which is standard 44khz but the audio is lowpassed around 19khz. Playback in audition seems to be stretching the audio resolution up into the 23khz area.

In regards to the original 8khz audio in question, it clearly appears that audition is doing something akin to cloning the original 8khz of audio into the next two 8khz sections of audio leading up to 24khz. At least that is what I am seeing in the spectral display. You can see this in this screenshot: http://img126.imageshack.us/img126/8123/audsy4.png

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Reply #2 – 2007-02-09 23:57:52

Quote from: Vchat20 on 2007-02-09 19:00:54

Oh. I also did some more testing and two different sound cards produced the same results here. And even playing back standard 44khz audio produced the same effect. I have an mp3 sitting here which is standard 44khz but the audio is lowpassed around 19khz. Playback in audition seems to be stretching the audio resolution up into the 23khz area.

In regards to the original 8khz audio in question, it clearly appears that audition is doing something akin to cloning the original 8khz of audio into the next two 8khz sections of audio leading up to 24khz. At least that is what I am seeing in the spectral display. You can see this in this screenshot: http://img126.imageshack.us/img126/8123/audsy4.png

The 8 kHz sampling rate (I should really write 8 kSa/s) allows only frequencies up to 4 kHz to be represented (Nyquist Theorem - half the sampling rate). If your spectrogram view truly represents the wave file, the top of the frequency graph should be labelled 4kHz. The 24 kHz on the screenshot indicates a 48 kSa/s sampling rate.

When downsampling from 44.1 kSa/s to 8 kSa/s, any decent software will have filtered out frequencies above 4 kHz to prevent aliasing of high frequencies into mirror frequencies in the 0-4 kHz passband. For example, a 5 kHz sine wave (1kHz above the Nyquist Frequency) would mirror down to a 3 kHz frequency (1kHz below it) if it isn't filtered out by a downsampling pre-filter first.

Likewise, when upsampling from 8 kSa/s to a higher sampling rate one should interpolate without introducing higher frequencies - i.e. post-filtering is necessary.

Anyway, you can see in your screenshot that weaker versions of the 0-4kHz spectrogram are mirrored repeatedly at successive 4kHz bands, upside down from 4-8kHz, right way up from 8-12kHz and so on.

Maybe Audition's spectrogram can only show 48 kSa/s so has resampled crudely to display it? I don't know the cause, but this stuff above 4 kHz cannot be present in the 8 kSa/s original.

Adobe Audition Nags

Reply #3 – 2007-02-10 00:04:10

No no no. You got it all wrong here. It's resampled the audio just perfectly. That's not the problem I have. I can downsample any audio file to 8khz and it will be reported correctly in the spectral display and once saved out and played back in a different program, it too sounds like it should. The problem I /DO/ have is when playing back that resampled audio inside of audition, it does it's own craptastic live upsampling for no real known reason at all. The image I linked above is a capture of what audition was giving me playing off that 8khz audio file in question. The capture audio file was done in full 48khz, 16 bit, mono. The issue in question here ONLY happens during playback inside of audition. Nowhere else.

Adobe Audition Nags

Reply #4 – 2007-02-11 00:19:15

Wow! That's a shocking bug for software like that. I don't have Audition (I have used the predecessor, Cool Edit however) so I can't help, but you might find some Audition user forums where you could ask other users for help in overcoming the internal resampler.

[Edit: it may well not be Audition's fault - I misunderstood the source of the audio we saw a spectrogram of - which is actually the output of the soundcard's DAC (output) fed back into its ADC (input)]

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Reply #5 – 2007-02-11 22:37:19

Quote from: Vchat20 on 2007-02-10 00:04:10

The image I linked above is a capture of what audition was giving me playing off that 8khz audio file in question. The capture audio file was done in full 48khz, 16 bit, mono. The issue in question here ONLY happens during playback inside of audition. Nowhere else.

Please tell us the exact steps you took to obtain this capture. It's exactly what you'd get if you played the file while recording the output of a Creative Labs sound card. In this case the card will resample to 48k on the fly. Unless you can prove that the captured signal has not passed through the sound card, we can't be sure that Audition is to blame.

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Reply #6 – 2007-02-11 22:48:27

Quote from: Dynamic on 2007-02-11 00:19:15

Wow! That's a shocking bug for software like that. I don't have Audition (I have used the predecessor, Cool Edit however) so I can't help, but you might find some Audition user forums where you could ask other users for help in overcoming the internal resampler.

Well, it would be if the problem was Audition, however we haven't established that yet. We need to know Vchat's exact signal path in obtaining that capture.

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Reply #7 – 2007-02-11 22:51:26

Well, I will admit that both the playback and capture were done on the same system. Audition did the playback while I captured in sound recorder. BUT, even with just doing regular playback and not recording anything, it still does the same thing audibly.

Adobe Audition Nags

Reply #8 – 2007-02-12 00:46:04

Quote from: Vchat20 on 2007-02-11 22:51:26

Well, I will admit that both the playback and capture were done on the same system. Audition did the playback while I captured in sound recorder. BUT, even with just doing regular playback and not recording anything, it still does the same thing audibly.

That could still be the fault of your soundcard and its driver - especially if it's Creative Labs (e.g. Audigy), many of which are known to resample all signals badly to 48 kHz. Frankly, this looks like the most likely cause of the problem, rather than Adobe Audition. That's assuming that the settings in your other apps (like Winamp) are resampling for you. You could try Foobar2000, enable DSP/Resampler and set it to convert CD-quality samples to 8000 Hz on the fly and see if it sounds as bad (it should if it's your soundcard and its driver).

Sometimes, Windows' Adjust Audio Properties (where you can set preferences for headphone listening, small PC speakers, etc. - try right clicking the volume icon in the system tray or go via Control Panel) allows you to choose (e.g. in Volume tab / Speaker Settings / Advanced... / Performance tab) the samplerate conversion quality. Best performs very well on the famous udial test on one of my PCs. If that option is available, it's what you ought to go for so that you can hear the proper sound while editing in Audition.

Adobe Audition Nags

Reply #9 – 2007-02-12 01:36:34

No, I don't own a creative card. The one in question here is an onboard sigmatel card. But I have also tried it with an onboard soundmax card in another machine which results in the same thing. And just for reference, the directound plugin on winamp on the soundmax machine reports supported playback rates of 8000hz to 48000hz.

And yes, I have the samplerate conversion quality in windows up to max. I often make sure all of that stuff is correctly set the moment I get a fresh install of the OS going.

Like I mentioned on another forum, I've got a few pci cards I can try and see if they do anything. I'll test that out later

Adobe Audition Nags

Reply #10 – 2007-02-13 19:57:59

Well, I just managed to test out this C-media CM8738 card here with audition. Now for this setup, keep in mind that windows is still utilizing the onboard soundmax card of this machine for everything. I kept it set as the primary card. Audition is the only program currently set to use the Cmedia card.

Very simply, I went through the same steps to downsampling audio to 8khz here and it gave me the EXACT same results as the other two cards. No change whatsoever. I even tried it with other resolutions below 48khz and the same phenomenon repeats itself.

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Reply #11 – 2007-02-13 22:32:42

Quote from: Vchat20 on 2007-02-13 19:57:59

Well, I just managed to test out this C-media CM8738 card here with audition. Now for this setup, keep in mind that windows is still utilizing the onboard soundmax card of this machine for everything. I kept it set as the primary card. Audition is the only program currently set to use the Cmedia card.

Very simply, I went through the same steps to downsampling audio to 8khz here and it gave me the EXACT same results as the other two cards. No change whatsoever. I even tried it with other resolutions below 48khz and the same phenomenon repeats itself.

So Audition is outputting to the C-media card, right? And you're then using Sound Recorder to record the output of the C-media using the C-media loopback as a source? And your headphones or speakers are plugged into the C-media card too? You then hear the same effects and record the same signal (with similar spectrogram)?

Is it possible in Audition to specify the output device (e.g. waveOut, DirectSound or Kernel Streaming)? If so, which are you using?

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Reply #12 – 2007-02-13 22:41:39

I haven't actually done any recording to get a visual on the cmedia device. I'm just going by what I'm hearing through headphones off the cmedia card which was identical to what I've been hearing all along up to this point which DOES differ to what programs like mplayer2 and winamp play back. Which I have recorded from those before INTO audition and as suspected, even recording at 48khz, the actual visible audio caps out at 4khz like it should.

Yes, I can set audition to use a specific card outside of windows' own settings. I dunno exactly how it works, but Audition uses its own output driver that I don't know exactly what it is offhand. I think it's ASIO based, but I'm not 100% sure.

EDIT: Here's the official tech docs on it at adobe:

Quote

Adobe Audition 2.0 installs an ASIO driver, the Audition Windows Sound driver, which is considered a wrapper (that is, an adapter between Adobe Audition, an ASIO application, and a non ASIO soundcard) for an existing DirectSound-compatible sound card installed on a computer. This ASIO driver is also the default driver selected for use when starting Audition 2.0 for the first time. The Audition Windows Sound driver provides no additional functionality beyond what is available through the DirectSound driver itself. In other words, if the DirectSound driver only supports stereo (two-channel) signal input and output then the ASIO driver will provide the same support.

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Reply #13 – 2007-02-14 17:39:33

Hmm. The ASIO wrapper info might be a clue.

Perhaps (pure speculation):

all your software except Audition passes the audio data as pure 8000 Samples per second digital PCM to Windows' Mixer, whose sample-rate conversion settings you've put at Best Quality.
Audition's ASIO driver passes the native 8000 sample/sec PCM direct to your soundcard

If that's the case, it could be that the soundcard's direct input is being fed with 8000 Sa/s audio by Audition. When directly fed with low bitrate audio, many soundcards simply lower the DAC clocking rate without modifying any characteristics of their reconstruction filter compared to that used for good quality output at 44100 or 48000 Sa/s. This creates essentially a staircase output with many harmonic aliases, and I think it is quite common among soundcards, possibly explaining why all three behave this way.

I remember using an HP Kayak PC (350 MHz, year 1999 or so) whose onboard soundchip exhibited just this behaviour, and I had to use foobar2000's resampler set to 44100 Sa/s to get decent reproduction of speeches at 8000 Sa/s.

Audition might assume that a user would only use higher-end soundcards which make appropriate adjustments (upsampling or selecting a better reconstruction filter) to deal properly with lower sampling rate audio. Equally, most people might be assumed to be working in 44100 Hz or more, where such problems would have little audibility.

On the other hand, if Audition does pass the 8000 Hz to Windows Mixer (which it sounds like it can't be doing, as Windows' Mixer is set to use your other soundcard, not the C-Media) the Windows Mixer ought to use Best Quality SRC.

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