Very bizarre behavior

[Rider]

I am using a common method of defeating auto gain control (AGC) in a camera by pumping a 19Khz sound into one channel while the mic is hooked up to the other channel.

In post, I'll delete the channel that has the 19Khz, even though in theory it cannot be heard. I tried it in Premiere Pro CS5 and Soundbooth, and in fact I cannot hear the sound on my headphone monitors.

But, I accidentally discovered that when the same file is played by Windows Media Player, the 19Khz sound is clearly audible ! (!!!)

I assume the Windows Media Player is screwing up somehow, but if isn't this a huge workflow problem. I mean, your sound editor and sound player don't interpret sounds the same way. How awful is that.

 

[ggrantly]

Rider,

Unless you have a specific reason to do what you are doing, you might try this as an alternative. If your cam will do so (most video cams will), record your single mic to both tracks. Record one track at a normal level, and the second track somewhere below, say less 10db. If you have any clipping in the standard audio, you can use the second track. If you don't need the second track, delete.

Grant

 

[Rider]

I am using a DSLR not a video cam. But note my post is about the anamoly that a file sounds different if played in Microsoft Media Player vs. Soundbooth.

 

[j1clark@ucsd.edu]

I am using a DSLR not a video cam. But note my post is about the anamoly that a file sounds different if played in Microsoft Media Player vs. Soundbooth.

A couple of things things occurred to me.

1) The stereo channels have some cross talk, and PP and SB may have low pass filters with cutoffs for the 'normal' human audio range, and MS Player doesn't...
2) While you indicate the procedure is to 'delete' the track in PP and SB, did you render out the file to a new file with only one of the 'stereo' tracks.

 

[Rider]

PP and SB may have low pass filters with cutoffs for the 'normal' human audio range

That would explain it, but you added the word "may" so I am not sure whether you believe it is the case or not.

As far as deleting tracks, what I said may have been confusing. At the end of the day, in the test I am listening to the unedited straight-from-the-cam file in both PP/SB and WMP. So both the mic channel and the 19Khz channel are present.

 

[j1clark@ucsd.edu]

That would explain it, but you added the word "may" so I am not sure whether you believe it is the case or not.

As far as deleting tracks, what I said may have been confusing. At the end of the day, in the test I am listening to the unedited straight-from-the-cam file in both PP/SB and WMP. So both the mic channel and the 19Khz channel are present.

Well, yeah, if in the MS widget you are playing the media that has both channels... well both channels will be heard. In PP and SB if you delete or mute a channel... you don't hear it while playing it in the editor...

 

[Rider]

To simplify things, please forget what I said about deleting channels. I am NOT deleting or muting channels in PP or in Media Player. The EXACT same file straight from the camera sounds different if played in SB/PP vs. WMP.

 

[Noiz2]

19K should be audible, at least by women and people who are young and have not spent too much time with cranked iPods.

Now possibly WMP is not filtering and isn't equipped to deal with high freq, in which case they are "rolling over" to something lower. OR the others are filtering below 19K?

Either way your not really defeating the AGC your just swamping it and eating up headroom with stuff your going to throw away. If you want to use a DSLR and have decent sound you need, NEED, to record to a separate recorder.

 

[Rider]

Either way your not really defeating the AGC your just swamping it and eating up headroom with stuff your going to throw away.

What makes you say that? The mic goes into the left channel and the 19Khz goes into the right channel. I throw away the right channel, which is not a problem unless I'm trying to record two channels.

 

[Noiz2]

The AGC is still there, the audio is still going through it you just over loaded it so it's clamped all the way down. I guess in a sense you have defeated but you haven't turned it off it's a little like "defeating" a bald tire by slashing it. Yes it's now a flat bald tire but you haven't really improved the situation, but you have defeated it's tire abilities.

That is probably over stating it a bit but the implication is that if you "defeat" the AGC you will end up with something resembling decent sound, and that isn't the case. The sound on the DSLRs sucks and there is no trick that is going to make it even barely acceptable for anything that matters. I've heard it used on some wedding videos etc, for B roll and it's OK, but only because it's not at all about the recorded sound. There is music and it's a verite moment so you can get away with it. For anything that needs better than home movie sound quality you need to go to a separate recorder.

 

[Rider]

The AGC is still there, the audio is still going through it you just over loaded it so it's clamped all the way down. I guess in a sense you have defeated but you haven't turned it off it's a little like "defeating" a bald tire by slashing it. Yes it's now a flat bald tire but you haven't really improved the situation, but you have defeated it's tire abilities.

That is probably over stating it.

You are right--that is overstating it! I can't turn my DSLR into a $3000 audio recorder, but the hiss is gone so that is a huge improvement.

I've heard it used on some wedding videos etc, for B roll and it's OK, but only because it's not at all about the recorded sound. There is music and it's a verite moment so you can get away with it. For anything that needs better than home movie sound quality you need to go to a separate recorder.

Did the wedding videographers have a dedicated audio pro? Did they go through the trouble of placing the microphones properly? Did they have good quality mics and were they using good preamps and setting the levels properly? Was the audio post-processed and mastered by a pro? As I've heard repeated on this forum, a $2000 Senn placed 20 feet from the sound will sound like crap.

 

[Noiz2]

Hey, do whatever you want. Go ahead and get a pro and all the rest and just record to the worst recorder you can lay your hands on??? If that makes sense to you go for it. I have worked on a fair number of DSLR shoots, some tried to use the on board recording and nobody has ever made it sound decent. Some were using the juice link AGC defeating thing some were using DSLR's that had adjustable gain, some had field sound folks who knew what they were doing some didn't. On the shoot that had an idiot mixer his sound was trash on camera and on stand alone recorder so it really didn't make any difference.

Point is I have heard a lot of tracks recorded in a variety of ways on to DSLR cameras and none has gone above the level of a good scratch track. If you toss a lot of experience and thousands of dollars of equipment at it it will I'm sure sound better. But why would anyone do that? If your spending that money get a recorder and get decent sound.

There are pretty much only two reasons to record on board (with the intent to use it). The first is because you have no $$, in which case your not going to be throwing experience and equipment at the issue so... sound is what it is. The second would be for logistics and your shooting something where the quality of the track is not that important. Wedding shots tend to be in that category. Your hero sound from the ceremony etc is going to be on something better but the wild B roll where you might want a sound bite can be so so and you need the flexibility and speed of a one man shooter.

 

[Noiz2]

I can't turn my DSLR into a $3000 audio recorder, but the hiss is gone so that is a huge improvement.

Point is you can't even turn it into a $100 recorder. A coma is a huge improvement over being dead, but it's still not good.

Did the wedding videographers have a dedicated audio pro? Did they go through the trouble of placing the microphones properly? Did they have good quality mics and were they using good preamps and setting the levels properly? Was the audio post-processed and mastered by a pro?

Just to make sure I understand this properly. Your point is that your advocating spending $10,000 or so (for a short) to avoid using a decent recorder? Because other wise your point is that you want to spend the money and deliberately go to a bad recorder that you can't monitor while recording. Neither makes any sense.

As I've heard repeated on this forum, a $2000 Senn placed 20 feet from the sound will sound like crap.

True. And that same mic placed properly and recorded on to a crap recorder will also sound like crap. The sound quality on the DSLR is about on a par with pocket dictation recorders. Most decent cassette recorders sound a lot better.

 

[j1clark@ucsd.edu]

The second would be for logistics and your shooting something where the quality of the track is not that important. Wedding shots tend to be in that category.

For most video setups that I've seen at the weddings I've shot (stills) the videographer will capture sound with a mic on the camera, even if the camera has a builtin. And then frequently they would use a handheld mic for personal interviews. (Obviously before HDSLRs...)

In addition, they'd often get the music list from the DJ and quite possible use a CD to do better on the sound than whatever they picked up via the camera mic.

Then then there was the vendor at the last bridal show I attended, who was shooting 8mm film... transferring to digital... to get a 'nostalgia' look... but I digress...

 

[Rider]

I appreciate everyone's input but we are really get off-topic. I personally never heard good audio on a wedding movie, and that was ages before DSLRs. But really, any idea why WMP plays back 19Khz sound so that the old and young alike can hear it? Did anyone else try this? Anyone wonder what else WMP might be doing to the audio?

 

[Rider]

Point is you can't even turn it into a $100 recorder. A coma is a huge improvement over being dead, but it's still not good.




Just to make sure I understand this properly. Your point is that your advocating spending $10,000 or so (for a short) to avoid using a decent recorder? Because other wise your point is that you want to spend the money and deliberately go to a bad recorder that you can't monitor while recording. Neither makes any sense.



True. And that same mic placed properly and recorded on to a crap recorder will also sound like crap. The sound quality on the DSLR is about on a par with pocket dictation recorders. Most decent cassette recorders sound a lot better.

The point is that you haven't isolated the cause of the bad audio. It could easily be due to any of the things I mentioned, and unless those things are done properly the audio will be sub-optimal regardless of the recorder. But if you want to argue about this, why not start another thread? I'll join you there.

 

[ggrantly]

Hey Rider,

In the end game, the folks here are trying to help you get good sound. Isolating your issue really doesn't matter to much because your audio workflow is pretty marginal to begin with.

Grant

 

[John Willett]

. I personally never heard good audio on a wedding movie, and that was ages before DSLRs.

That's a shame as there are plenty of wedding videographers doing good sound - for example, using radiomics to get the priest and vows, etc.

A wedding videographer that only used an on-camera mic. I would consider not worthy of hiring.

 

[Rider]

Hey Rider,

In the end game, the folks here are trying to help you get good sound. Isolating your issue really doesn't matter to much because your audio workflow is pretty marginal to begin with.

Grant

Grant--I honestly don't know what you're talking about.

 

[Richard Crowley]

any idea why WMP plays back 19Khz sound so that the old and young alike can hear it? Did anyone else try this? Anyone wonder what else WMP might be doing to the audio?

Consumer players like WMP, and others play games with the audio signals. It doesn't surprise me at all that WMP is hetrodyning the 19KHz signal down to some lower (audible) frequency. WMP is not suitable for the application you are trying to use it for. And your unconventional workflow is simply revealing this anomaly.

I question the practice of attempting to play your kludged audio signal on WMP in the first place.