General Audio Recording Thread

[Chippy569]

Originally Posted by Channel One

The difference between the AGC and ALC in the case of the Canon T2i rather simplified is;

Traditional AGC works on the basis of having a steerable analog amplifier in front of the analog to digital converter usually within the same chipset, a processor analyzes the output of the A/D device over a set period of time and if the output remains to low the gain of the amplifier is increased, if the output of the A/D is too high the gain of the amplifier is reduced, this keeps the signal being converted from being clipped by the A/D which causes distortion, a very nasty sounding distortion.

With ALC in the case of the T2i the gain of the amplifier is pre-set and the quantization of the A/D is altered, if the input signal is to low the dynamic range of the A/D is expanded in an attempt to pull the lower signal more to the middle of the digital range (128), if the input signal is too high the dynamic range of the A/D is compressed in an attempt to pull the higher level of the signal closer to the center of the digital range to prevent clipping.

The end result with that version of ALC is when the input signal level is low the dynamic range is considerably higher and the inherent noise floor is as well, hence the reason some folks complain about the digital recordings from the T2i being noisy, conversely when the input levels are high the audio is excessively compressed reducing the dynamic range which is also undesirable.

The solution is to ride the gain before inputting the signal into the camera keeping it as close as possible to 0 dB which drives audio guys bonkers as they are trained to keep the levels down by 6 to 12 dB to allow enough headroom to prevent clipping.

Make sense?

Wayne

good explanation.



just want to make sure this H4n user guide gets posted in here: http://photography-on-the.net/forum/...d.php?t=988677

[Channel One]

Originally Posted by Chippy569

good explanation.

Thank you, considering your background I appreciate that comment.

By the way even though we utilize shoulder/tripod mounted Panasonic or JVC HD camcorders for the events we cover and in most cases map audio from the board into them I still drop audio via an active splitter to a H4 left next to the splitter, this allows me a easy and reliable way to forward event audio to our AM side producers without interfering with the NLE guy and his producer.

Wayne

[Channel One]

By the way to the person who e-mailed me and whose screen name will remain unmentioned, my post was not intended to be any form of Canon bashing it is simply a description of a system that is in my opinion a less than desirable method of recording audio.

For the record I am a rather rabid Canon supporter having used their equipment since the T-50 and for what it is worth my business partner utilizes 7D’s for video though being old school I am still stuck on shoulder supported camcorders.

Wayne

[Chippy569]

Originally Posted by Channel One

By the way to the person who e-mailed me and whose screen name will remain unmentioned, my post was not intended to be any form of Canon bashing it is simply a description of a system that is in my opinion a less than desirable method of recording audio.

Wow, that's kind of silly to get on your case for that, lol. AGC is bad, ALC is bad but not quite as bad. With either case it's very difficult to undo the volume changes and get back to a normal volume. Manual control needs to be set properly but after being done it'll be much, much easier to use in post. Not giving some of the cameras the manual option is a very frustrating limitation on Canon's part since it's probably all of 5 lines of code in the firmware.

[SaxonIV]

Originally Posted by Chippy569

Wow, that's kind of silly to get on your case for that, lol. AGC is bad, ALC is bad but not quite as bad. With either case it's very difficult to undo the volume changes and get back to a normal volume. Manual control needs to be set properly but after being done it'll be much, much easier to use in post. Not giving some of the cameras the manual option is a very frustrating limitation on Canon's part since it's probably all of 5 lines of code in the firmware.

I completely agree. if its just marketing, it just ticks me off. i'm sure its only a little issue but would sure be nice to have it work.

[reappear]

Hmm... A question popped up in my head:

What's the ideal* workflow for audio post processing? *your way

Let's start from the situation where you have taken the video and you have recorded the audio with a recorder+preamp+mic combination... now what?

[Chippy569]

Audio work flow depends a bit on where you're doing your editing, for example the workflow in Final Cut + Soundtrack Pro is much different than Premiere + Audition is much different than Avid + Protools is much different than Sony Vegas + Audacity. However, generally for me the rule is:

1. A/V Sync. This is usually done in your NLE.
2. Export to your audio editor. If your audio editor is your NLE, then nevermind this step.
3. Edit!
4. Bounce to your desired output tracks. If it's just youtube I use just a stereo L/R. If it's bigger I'll have a music stereo track, SFX stereo track, and two dialog tracks (one stereo, one mono). If it's going to surround sound then there would be rear music and SFX tracks.
5. Re-combine your audio and your video in your NLE.
6. Print video and enjoy!

[reappear]

Originally Posted by Chippy569

Audio work flow depends a bit on where you're doing your editing, for example the workflow in Final Cut + Soundtrack Pro is much different than Premiere + Audition is much different than Avid + Protools is much different than Sony Vegas + Audacity. However, generally for me the rule is:

1. A/V Sync. This is usually done in your NLE.
2. Export to your audio editor. If your audio editor is your NLE, then nevermind this step.
3. Edit!
4. Bounce to your desired output tracks. If it's just youtube I use just a stereo L/R. If it's bigger I'll have a music stereo track, SFX stereo track, and two dialog tracks (one stereo, one mono). If it's going to surround sound then there would be rear music and SFX tracks.
5. Re-combine your audio and your video in your NLE.
6. Print video and enjoy!

Do you mean that I should cut the audio/video to match before I start the real editing?

What are the things I should do in Audacity?

[Chippy569]

Yes, if you have multiple audio/video tracks it would probably be beneficial to bring them all into your NLE and sync them all up. Then you can trim to just the clips you want and only edit what you need to. It'll save you time and filespace.

Once you have all your clips synced your NLE should have a way to either do an audio-only export or maybe launch your audio editor straight from the clip (ie in final cut you can right-click the clip and select "open in external editor").

Then do your edits in audacity and save your file. Make sure your save format (bit depth, sampling rate) is the same as your input.

Re-import to your NLE and enjoy.

[reappear]

Thanks for the info!

Are there any guidelines what you should never do when editing the audio?

[Chippy569]

uhh, never put a limiter on your output with the output level at 0dB FS and the threshold at -infinity.

Oh, never forget to listen to your stuff on a couple different speaker systems. Compare it to other similar material, if you can. You know those TV commercials that sound like they're blasting at you at a million dB -- avoid that.

[nolimits882000]

Not sure what kind of NLEs people are using, but I came across a piece of software called PluralEyes, meant to sync audio recorded separate from camera. It's what I started to use since I got my 60D and the only thing you need to have enabled is your onboard mic so it has audio to sync with.

There's also a version that doesn't necessarily need Final Cut Pro, so other NLEs will work with it too. Just my easy way of getting audio synced, and I'm looking to purchase the H4N for filming

[des34415]

Originally Posted by H2OSkier

I'm pretty new with the video thing. I had done a couple of little projects using a 5D, 7D, and a Zoom H4N. I was worried about syncing the audio but I purchased DualEyes and it's been more than I expected. DualEyes is just way too cool. It is a stand alone product that is independent of the editing software you are using. I'm using Sony Vegas Movie Studio 10.

I just did a 15 minute project that had 20 video clips and seven audio clips. Some of the audio tracks were for more than one video track. I just loaded those into DualEyes and told it to replace the audio tracks in the video with the stand alone tracks. DualEyes figured out what audio tracks went where and created new video files with the new audio. It even included the name of the audio track it used in the name of the new video clip (you know what audio track that was used). The whole process took less than five minutes.

I also just found a wired lapel mic ATR 3350 for $25 that is pretty nice for the money.

I've learn quite a bit so far but have a LONG way to go.

Ken

hi there,

could i just confirm dualEyes can sync audio and video in batches without us manually matching them 1 for 1?

i always have many short clips ( 10s approx ) and am intending to leave the zoom h1 running (after i buy it, that is) while i start/stop my videos. would there be any problem syncing with dualeyes?

another question - what is the purpose of connecting . 3.5mm cable from the H1 to the DSLR? is there any benefit as compared to just recording without the cable and syncing in post?

another comment i came across was : the audio quality on the zoom h1 if set to similar settings (48kHz, same to t2i internal mic ), would be the same as the internal mic. is that true? i have ML installed and hence don't have much of the hissing problem. most of the youtube video tests are done without ML so the comparison isn't what i was looking for. any thoughts? (sorry if it's been posted before! )

lastly, would this foam windshield fit the zoom h1 head? looks a little big but i'm looking for a low cost shield!
http://cgi.ebay.com.sg/2-x-windscree...item2c5840c574

[Channel One]

Originally Posted by Chippy569

Oh, never forget to listen to your stuff on a couple different speaker systems. Compare it to other similar material, if you can. You know those TV commercials that sound like they're blasting at you at a million dB -- avoid that.

I come from a different school of thought when it comes to perceived loudness that being a video which is perceived as being louder than average is a better video than one that requires the listener to crank up the volume.

Now that is not to say a low level (at times for dramatic purposes) is not permissible but overall a video that has a good punch will win out with viewers every time.

Of course one must be careful to prevent changes in perceived loudness within the production if it does not serve an artistic or dramatic purpose as that is the mark of a duffer but again generally speaking the “louder the clip is perceived the better clip is received.”

Now achieving that goal can be burdensome requiring a bit of extra work in post and requires a well trained ear and a few additional few devices (equalizer, compressor, processor, Dorrough meters) to be able achieve that goal but the end result can make the difference between a yawner clip and a winner.

Wayne

[reappear]

Originally Posted by des34415

another comment i came across was : the audio quality on the zoom h1 if set to similar settings (48kHz, same to t2i internal mic ), would be the same as the internal mic. is that true? i have ML installed and hence don't have much of the hissing problem. most of the youtube video tests are done without ML so the comparison isn't what i was looking for. any thoughts? (sorry if it's been posted before! )

Actually I did comparison by mistake when I was recording a singing competition once with the H1 and 550D (T2i). In that place the quality of T2i mic totally surprised me. I think I had ML installed by that time too. Camera and H1 were in the same location and the loudspeakers and singer were about 10m away. H1 had more dynamic sound and deeper bass sounds, but it wasn't like day and night in that situation. But it was quite controlled place and H1 has been fantastic in other places.

Tho' I just got H2 too and it's so different to use. Both H1 and H2 have their own pros and cons. I'll be using both whenever I need them.