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TommygunZA

SD 633 MP3 recording Sounds lousy

29 posts in this topic

I recorded one of my files as an MP3 on my SD633 and I must say the playback on the SD sounds pretty shocking. I recorded at 192kbps and it is all artifacty and has those high pitch squiggly sounds. It sounds vaguely better played on my PC. Is this a standard thing with the 633? Currently  Im just taking the wav files and encoding them using Audacity and they sound a million times (well at least twice) better than the native MP3s. Im going to have a shot with 320kbps and see if its any better.

Has anyone else noticed this? Im only trying as a client wants stuff as MP3.

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That's a bit surprising, although I've never had a reason to record MP3. Suppose you can always just convert to MP3's on your computer.

 

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Reload firmware and restart using factory settings.   This happened to me... it took awhile to figure out but there were other anomalies as well.  Limiters activating with fader closed - weird stuff.  

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Gosh...thanks John, Ill give it a go and report back.

 

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As well, it's probably good practice to reformat your cards after a firmware update.

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It's weird. The above are on target. In a simple universe, transcoding mp3 file to wav files don't get you any advantage.

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Reflashed my SD633 from 4.50 to 4.51 (at least I got an update out of this process). Did a factory reset and proceeded to record to my (reformatted) SD card (approved media) Did some recordings at 192kbps and have exactly the same artifacty squiggly sounds in the background (its not massive but it is there) Did the same on my Zoom H4n (mp3/192kbps). No artifacts on the Zoom recording (admittedly higher noise floor). Its not a train smash as I mentioned, I can take the ISO's and encode to MP3 on my PC I was just kinda expecting better from Sound Devices? Id love it if any other 633 users gave it a go and reported back.

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Have you contacted sound devices?  Perhaps your the lucky person that discovered a possible bug?

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(ambivalent smiley face) 

Good point, ill mail em now.

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I've opened a ticket with SD and they suggested exactly what JohnGooch said I should do..which didn't help. Could I ask any of you who have a mixer (SD633) and mic close to hand to try record a brief  MP3  and have a listen to see if you get the artifacts too. It would make trouble shooting a lot easier if there are a few SD633 owners with the same problem. Ill report back if the SD help desk sort me out.

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It would make trouble shooting a lot easier if there are a few SD633 owners with the same problem. Ill report back if the SD help desk sort me out.

I have tried this now with my 633 and can confirm that I have got some very noticeable artifacts even at 320kbit/s.
Have you heard back from SD yet?

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I just did a test on mine, close voice in an ambient neighbourhood with leaves rustling and distant traffic.  At 128 I had a few unexpected and shocking warbles on the voice.  The background ambience was somewhat squiggly, but about what you would expect at that bit rate.

At 320, the same test sounded OK, less squiggly in the ambience and no warbling on the voice.

Not exactly a scientific comparison to whatever you guys are doing recording for your tests, but some feedback anyway... - I thought 320 sounded all right, but I expected better from 128...   With Mp3's I expect a loss of resolution and some squiggles on high frequency complex sounds (like water or tree leaves), but the large warbly artifacts on voice were unexpected.

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Well, that's a recording being made in 128, as opposed to a downconvert from 24/48 wav to 128.  The latter sounds a lot better.  I have podcast etc clients for whom my deliverables are MP3s, we never record in MP3, we only use downconverts and the sound is quite good.

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Yep, based on this experiment, that's the way I'll be doing it if I need to deliver MP3-  any thoughts on why a raw recording to Mp3 would be so much worse than a downconvert?

Cheers,

Brent Calkin

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Good Q for SD.  Do Zooms or etc recorders sound good when recording in MP3?

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SD (and others here) will know. But I'd guess the real-time recording to MP3 might require a few processing shortcuts, or at least more than the 633's chips can spare without shorting other processing needs...

What's the real answer?

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From experience, there are plenty of gotchas when tuning a real-time MP3 encoder.  TASCAM has been doing it since the PocketStudio 5 in 2003, when the available processors were seriously lacking in power compared to what is in use now.

Squirrily sound can be caused by not filtering LF, only recording one channel when using Joint Stereo or Stereo, (should use dual mono); or recording at low level, which can confuse the encoder.   
128kbps (stereo) should be enough, 320kbps should be pristine.   It's only when you go down to 96k or below that the result is never going to be good enough.

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Probably the encoder software SD put in it. I've had excellent results using the Mainconcept and LAME MP3 encoders. I prefer the Mainconcept when very low bit rates are needed (64kbps and below for small file sizes). The WinLAME RC3 encoder has a fast and easy batch process and the option for HP and LP filters (among other parameters. Most of the advanced audio user parameters have to be be set in a 'script' file which become a preset.  Neither writes a TC stamp though, so put LTC on an audio track if needed

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I don't think it's the encoder per se. I don't think I have recently heard an mp3 file this bad.
I think it's the real-time part of the operation that's making it difficult for the recorder.
I bet if the recorder recorded the track as .wav and converted to mp3 after the recording stopped, it would sound much better.

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3 hours ago, Rick Reineke said:

Probably the encoder software SD put in it. I've had excellent results using the Mainconcept and LAME MP3 encoders....

But aren't those running on your computer, with a comparatively big CPU? I'm guessing SD had to balance speed with available processing power....

But interesting reports and comments from Tommy, Tom, Constantin, and everyone. So about the quality of the MP3, are you saying it's not so great for transcription, or not good enough for backup to your wav files? [edit- to be clear, I'm not thinking of MP3 as a regular backup file...just trying to get a sense of how good/degraded the MP3 files sound]

Would love to hear from SD on this, since I'm heavily leaning towards buying a 633 (ya, I'm behind the times...still getting by with 744T) or something similar... This probably wouldn't be a deal killer for me, but would be interesting to know...

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It would be fine for transcription- and that's the only reason I've ever had for Mp3 delivery.  No good for backup.

Cheers,

Brent Calkin

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If you wanted a backup , the machine as you know should be set to more .wav files on the SD card.....    If for transcription ... even if there are a few burps, probably not a big deal, but agree with others, just convert from wav to Mp3...  

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Fortunately haven't had the need to do mp3s on my 633 but sure glad I read this thread. Hope SD gets to the bottom of this.

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The mp3 recording is absolutely fine for trancription, which is it's main purpose anyway, I suppose, so it's not a really big issue at all. It shouldn't stop anyone from buying a 633.
It will only record the LR mix tracks as Mp3, not the Isos, so it's not ideal as a backup format.

Couldn't the 744 record mp3 files, too? How does this sound?

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On 5/26/2017 at 6:15 PM, afewmoreyears said:

If you wanted a backup , the machine as you know should be set to more .wav files on the SD card.....    If for transcription ... even if there are a few burps, probably not a big deal, but agree with others, just convert from wav to Mp3...  

Ya, that was just poor wording on my part. I was just trying to set a couple benchmarks to help learn how "lousy" the 633 MP3s were...

And, yes the 744T can record MP3; I've just never done it....

Anyway, Tommy, if you hear back from SD please fill us in.

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