Pay Close Attention to Your Audio in HDV

General Discusssions for Audiography
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Paramvir Singh
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Pay Close Attention to Your Audio in HDV

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Pay Close Attention to Your Audio in HDV
HDV has an MPEG-1 layer II audio format that records at 384 Kbps. This is very close to CD quality audio, except that it’s 48 KHz rather than 44.1. This compressed format is one that many HDV naysayers decry, but it’s perfectly useable for most shooting scenarios. However, acquiring audio at too low a level is like shooting images at too low a resolution. This becomes a problem when the audio is processed. Therefore, acquire audio in the HDV realm, as loud as possible without crossing the 0 dB brick wall. Level processing is a challenge in all formats, but HDV audio is slightly less forgiving than PCM audio (the DV standard). Therefore, you’ll want to pay closer attention to the audio if you’re shooting HDV.
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Re: Pay Close Attention to Your Audio in HDV

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Sort Out Your Audio Sync Issues
The HD format is still evolving, so it pays to discuss some of the technical aspects up front before production. If clients start discussing surround, then we talk about all the possibilities. For example, if they’re getting custom music, we ask for the stems of the musical instrumentation so we can have a lot of fun with the mix.

The other thing that we discuss is what their palette is— it’s unreal the amount of control and flexibility that you have in surround. If we take the ambience, for example, we can really add some cool perspective change, throwing a sound effect over here or over there.

It’s important to focus on sync issues. This is where HD could be challenging to people. There’s not just one flavor of HD. There are not only different resolutions, but seven or eight sync rates— 60i, 59.94, 30, 30p, 29.97, 29.97p, 24, 23.97. When you’re on location and shooting film and you’ve decided to edit HD, you need to be specific about what HD format.

The first thing to consider is where it’s going to air or if it’s for theatrical release. The networks have different technical operations specifications (TOSs), often 30 to 40 pages long, and if you want to know how they want their 5.1, you’ve got to read that. PBS is different from Discovery, which is different from Fox.

Is it for theatrical or television or both? If it’s both, that means different scan rates, sync rates, and aspect ratios.

Basically, if you shoot in 24p, you have to edit in 24p. You can’t go from 24p to 29.97 and back to 24p again because your audio will be out of sync. If you do a Dolby E mix, you need to know that the encoder, which turns your 5.1 mix into digital information, delays by one frame and then the decoder, which turns it into an AES stream, delays it another frame. So when you go through encode/decode, you’ve delayed two frames. What you need to do is offset your mix two frames.
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Saihmee Dara Singh
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Re: Pay Close Attention to Your Audio in HDV

Post by Saihmee Dara Singh »

have recorded on hdv and its quality is like recording high bitrate mp3 audio(compressed) ...i wud suggest recording on a recorder which records uncompressed audio at 16/24bits and 48k/96k sample rate....wat say ?
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Re: Pay Close Attention to Your Audio in HDV

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how bad is the quality to work on post dara?
what about Docus? do documentary crews absolutely have to take external pro audio recorders for critical interviews in noisy areas?

check this hot stuff for recording pro audio on iPod:
http://ftiipeople.com/index.php?option= ... topic=77.0
Nikhil Mulay
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Just worked on HDV...

Post by Nikhil Mulay »

Just finished doin a short film on the Sony HDV- Z1U and the quality is not too good i must say.  To start off with the mic pres totally suck; you can hear the noise even with no mic plugged in!!! Plus the response is not too good; slightly lumpy i must say with a hump in the mids. Playback was more of a disappointment though with low level information losing out on crispness and definition, say goodbye to all that awesome ambience you thought ya had gotten. Lets see how it works out in the post though. Aside from this, i think it should be pretty decent for docus though, with dialogues coming out decently clear. But if audio quality is critical, id say carry a seperate recorder.
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Re: Pay Close Attention to Your Audio in HDV

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i too have been disappointed by the audio quality of HDV. nikhil, good advice. i hope people with critical audio requirements are reading this one.
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Re: Pay Close Attention to Your Audio in HDV

Post by Nikhil Mulay »

Well... finished working on the short film sometime ago. Audio quality is ok... not too great but usable nonetheless... A few issues with hdv sound though... ambiences go for a toss, theyre there but not the crisp clean ambience that we get on better recorders... just a peaky mids kind of ambience... and distortion is all to apparent as we approach 0dbfs, there is absolutely no headroom!!!
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Re: Pay Close Attention to Your Audio in HDV

Post by Nikhil Mulay »

oh yes.. one more thing, even though the audio was recorded on the camcorder, some shots did go out of sync; and horribly out of sync, something like 20 frames or so. Absolutely no reason why this should happen, but it did!!!
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