Zoom H2 VBR encoder

Discuss the Zoom H6, H5, H4, H4n, H2, H2n, and H1. Please don't "post and run". Participate in the discussion. Thanks.
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SerDanTwo314519
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Zoom H2 VBR encoder

Post by SerDanTwo314519 » Mon Oct 01, 2018 2:31 pm

Hi,

The Zoom H2 and probably some other models have a "VBR" mode in the mp3 recording settings. Unfortunately, these settings are not specified any further in the manual. I'm pretty sure Zoom doesn't use LAME for licensing reasons, and what VBR mode really is on the H2 doesn't get a lot of attention on the internet. For posterity's sake, I figured I'd briefly post what I know. This is a wonderful forum for the Zoom mics, after all.

I ran three quick tests to get an idea of the range of bitrates the Zoom H2 uses for VBR. All tests were ten seconds long. The first test involved recording from the line-in using a dummy auxilliary cord (nothing connected on the other end), which should pretty much be dead silence. The second test involved jingling some keys continually in front of the mic from beginning to end. The third test involved speaking into the mic, reading random text on the internet from beginning to end.

There's not a lot of tools out there that dig in and analyze VBR files in a detailed manner, but the program mp3packer provided the bitrate distribution info that I was interested in. Looking at the output mp3packer provided, I got a general sense of the range of the VBR encoder across each of the three tests.

The jingling keys test should invoke the highest bitrates for any decent VBR encoder, and it turns out that the largest distribution of the bitrates fell between 128-160kbps, with more of the bitrates distributed at 160kbps rather than 128. Next, as one might expect for dead silence, the VBR encoder recorded silence at a solidly low 50-64kbps. For the recorded speech, the VBR encoder put the majority of the bitrates at around 96-112kbps, but mostly at 96kbps.

Scouring various sources on the internet, a number of people have suggested to use the VBR encoder for non-studio outside recordings if wav recording is not ideal due to limited space. I can see why this recommendation may be the case, since at its best VBR will be better than, say, 128kbps, which is an arguably low bitrate that a lot of non-audiophiles can detect artifacting in. Note that because I'm pretty sure Zoom didn't use LAME, I can't speak for the psychoacoustic model they used for deciding what bitrates to use and when to apply them to optimally mimic the source material. But again, judging by impressions from various folks on the internet, it doesn't seem so bad that it adversely affects the quality of outside recordings. Some musicians swear by the H2 VBR encoding, and I can see now that in many respects it's not a bad deal.

In any case, long story short: The Zoom H2 VBR setting has a fixed range from 64-160kbps. With a small SD card, or for long trips, VBR is good to use if your desired mp3 settings are somewhere less than 160kbps. This is because the highest bitrate the Zoom H2 will ever use in VBR mode is 160kbps. So don't even think of using VBR if you like 192kbps and don't care about the space!

Disclaimer: I didn't spend months making this test, so who knows, perhaps some numbers are inaccurate. But what I will say is that for my Zoom H2, and for my SD card, these were the results that I got, and what I'll personally keep in mind when using the Zoom H2 moving forward :)
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Re: Zoom H2 VBR encoder

Post by Jim_Fogle » Tue Oct 02, 2018 8:38 pm

I don't have a H2 so I'm unable to run any tests however I have to believe such a test should include a 20 to 20,000 hertz frequency sweep at a constant volume level and a pink noise sound at a constant volume level.

The frequency sweep shows how the VBR handles hearing range frequencies while the pink noise shows how the VBR handles frequency clusters.

I like the other tests you made, I just think the additional tests I described will provide more information.

By the way, the digital recording software Audacity includes ways to record silence, frequency tones and frequency sweeps. The only thing I haven't figured out how to create in one step are 3 db volume modulated 1,000 Hertz and 10,000 Hertz test tones for creating calibration tapes.
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