Increasing the bitrate - does it do anything?

[KarelBata]

I assume it does, or the ML team wouldn't include it? 

I can't say that I've noticed any difference, but in the meantime I leave it on 1.8x just in case there's something good going on I can't see, but that has an influence further down the pipeline. I do a lot of manipulating in post and anything that increases quality is welcome.

Anyone able to comment? 

[1%]

Default bitrate is very low. Like ~45... Seems a decent balance is 60-70.. in the high 70s/80s the camera runs out of buffer often. Also, ISO affects your bit rate so 1.8x may not work all the time. I leave it around 1.4 so I can shoot higher ISOs and scenes with more motion without any unexpected crashes. In a controlled environment you can set it higher... in darker scenes you can set it higher and at 80 ISO you can set whatever you want because I had no problems even at 3.0x

The 40s look not much better than an HDV camcorder.. the 60s+ look very good indeed.

[ilguercio]

I can't see any difference and many tests have proven the same.

[1%]

Got a link to one? I throw everything in post and like the higher bit rate files. I've dealt with a lot of HDV footage and the low/default bit rates look a little worse while the higher stuff seems to look more detailed. I see a difference on the bike shot in the wiki too. Its very subjective and final footage will be much lower/more compressed anyway.

Would be nice to test on green screen with motion blur.

[Arthur]

I will find out when I test it on my 1100D. Compression artifacts are though on this one (due to the 720p limit for shooting)
Sharpening and noise removal are hell thanks to the low default bitrate, since it can't get off by having more pixels, the video lose a lot of detail and since some heavy sharpening is required in order to try to restore some detail, it makes the compression stand out even more.

[clausfrederiksen]

It is always an aim to get as high bitrate as possible/with the hardware limit. No matter if you shoot on dslr, XDcam, P2 etc.

HDV is about 28/30 - the lowest of them all, in the HD world. And its not impressive.

The higher the bitrate, the better color, more "sharpness" (... in the good way, and not resolution). Its gives you much better possibilities for color grading, fixing stuff - lowlight/highligt faults etc.

You might not be able to see the difference right away, looking at the raw material  - but when being creative, fixing stuff and colorgrading - you will feel it, and see it very clearly. And it will open up a world of possibilities thats not technical possible with low bitrates.

So keep it high - in the edit its too late to fix things, if the bitrate was too low while shooting.

[1%]

Sharpening and noise removal

I'd turn that off if possible. Do it later in post with real processing power.

You might not be able to see the difference right away, looking at the raw material

A green screen test with moving subjects or hair would be an interesting comparison.

[clausfrederiksen]

A green screen test with moving subjects or hair would be an interesting comparison.

  

With a bitrate at 60-70, vs. 25-28 - its guarantied to look better. And make your croma key nice and easy, not only to look at, but also to work with. Shooting green screen demands three things (... amongst a few more), to be succesfull:

1. The right kind of lighting.
2. High bitrate as possible.
3. The right kind of key software.

But a test is always interesting, if not - just see why a high bitrate is good stuff 

[1%]

Still only 4:2:0 on all of these cameras... intermediate codecs help but they are mostly lies. Lighting I think was the biggest thing for green screen as I could pull decent keys off of HDV.

But I wonder 1.0x vs 1.8x what kind of difference it would make. You lose audio after 1.2/1.3x thus far.. wonder why nobody has tweaked the audio part of the encoder.

[clausfrederiksen]

But I wonder 1.0x vs 1.8x what kind of difference it would make. You lose audio after 1.2/1.3x thus far.. wonder why nobody has tweaked the audio part of the encoder.

Hmmm ... interesting fact. Maybe its worth a try after all 

[sparx.ger]

Is this true? You loose the audio? Maybe you should record the audio external...

I think this is a bug! Increasing the bitrate in order to loose the audio?!?!?!?

[John Kesl]

Is this true? You loose the audio? Maybe you should record the audio external...

I think this is a bug! Increasing the bitrate in order to loose the audio?!?!?!?

Seriously bro, you need to do some reading of the users manual and the forum before you post. The Bitrate goes up and the sound drops out, does that not make sense to you? It's no bug, it's a by product of overclocking the processor.

[John Kesl]

I assume it does, or the ML team wouldn't include it? 

I can't say that I've noticed any difference, but in the meantime I leave it on 1.8x just in case there's something good going on I can't see, but that has an influence further down the pipeline. I do a lot of manipulating in post and anything that increases quality is welcome.

Anyone able to comment? 

What camera you use, the ISO and the card in it are important. If you use lower ISO, bitrate will not increase as much as high ISO. Also, on my 60D with 95Mb/s card I can pull 1.5 -1.6 up to 1.7 but any higher and the gains are minimal. If you set it to 1.8 you may or may not be getting 1.8. I would do the minute test. roll 1 minute on the same scene whilst adjusting the ISO and bitrate to see which combination of what yields the largest file size, write down those settings and then test them at different CBR to see how much file size you get. The most I've got so far on my 60D is 521MB for 1 minute of footage. And I can see a diff in AE doing color and look. The gradation is smoother.

[KarelBata]

Interesting advice John (and everyone else).

I still don't see how an increase in bitrate or file size will automatically improve the picture quality. All you may be doing is recording the same thing but with more bits! Rather like transcoding HDR to a huge ProRes4444 file and thinking you've somehow improved the original.

I've also never heard of how changing the ISO changes the bitrate. How does that work? (See? I'm not a copmplete know-it-all  )

I'm using a pair of 600s (I shoot video in stereo 3D) with Sandisk Extreme Pro cards. If I need sound I use an external Marantz PMD660 recorder. It's not sync, but it does the job, and I don't do long takes.

[ilguercio]

Iso changes the bitrate because of the noise, same way a RAW file shot at 12800 iso is heavier than a shot at 100 iso even if the former is crappy.
Noise has to be recorder, and so it burdens the file.

[SuperHans28]

I tested it today, I test both 1.0 and 1.4 and imported it into Premier Pro, it had the same average data rate (Premiere doesn't display it the same in format). What I shot didn't have any movement in or anything so presumably why the bit rate was the same.

When I did a test ages ago with the Q-Scale adjustment, I uploaded a PSD to compare - http://www.mediafire.com/?1131udow967dn9q
I found I could get 85mbps the most on the cards I was using at the time (Class 6 I think). It was no means a scientific test. On that version I think you had to disable sound, global draw etc to get that high.

I'd like to be able to get 60/70mbps with sound and global draw on but I don't think you can?

The people who are saying they cant see much difference, have you checked the data rate/bit rate of the file to see if it is actually different?

[1%]

no no no,

Bitrate goes up and the sound drops out, does that not make sense to you? It's no bug, it's a by product of overclocking the processor.

Sound doesn't drop out. There is not enough write speed or buffer space to do 40mbps of audio + 100mbps+ of video. You will have audio at any bit rate if you get a card with >20MB/s write (wait a bit). I can do audio unstable at 3.0x even. Just recording stops quickly when the buffer is over.

I still don't see how an increase in bitrate or file size will automatically improve the picture quality

You must not post or encode video much. Higher bit rates = more data... unless the encoder mismanaging use of that high bit rate (which I think it is right now). That is why the gains aren't so "great". Higher bit rate = less compression. Like 320kbps mp3 vs 128kbps mp3. When we set I/P/Gop Opts/Gop size it should be more noticeable & useful.

60D with 95Mb/s card

What is your sustained write speed? Regular mode. I have no problems with 2.0x even at high ISO. My write is 15-18MB/s

I've also never heard of how changing the ISO changes the bitrate.

Sensor sensitivity. More light = better exposure = more data. At 5k iso bit rate gets really high, over the 100s. Its not just noise. You'll also get higher bit rates by adding more light at the same ISO (until you go over). A dark ISO 320 is like 20Mb/s. At ISOs below 100 data is being rejected so bit rate is extra low even when well lit. You can see the same stuff in your raw files.

I'd like to be able to get 60/70mbps with sound and global draw on but I don't think you can?

60, easy.... 70 no. Global draw makes no difference for me. Its always on with histogram, peaking + zebras.

[KarelBata]

This is getting mightily confusing.

SuperHans, I downloaded your file to, as you say, compare. But what exactly am I meant to compare it to? It looks good, but compared to what?

1%, As it happens I've posted and encoded a lot of video. A large file size, or bit rate, doesn't mean anything in itself. You're just playing a numbers game. Check out this graphic taken from http://www.streamingmedia.com/Articles/Editorial/Featured-Articles/Encoding-for-YouTube-How-to-Get-the-Best-Results-83876.aspx

[SuperHans28]

This is getting mightily confusing.

SuperHans, I downloaded your file to, as you say, compare. But what exactly am I meant to compare it to? It looks good, but compared to what?

Well you can select the different bit rates on the layers, turn them on and off, and you have to zoom in to see any difference really, the main thing you can notice is how less blocky it looks the higher bit rate.

I would usually just stick with the default bit rate Canon uses.

[KarelBata]

Ah - you mean open it in Photoshop? 

I thought it was a bit big!

So what's the 'normal' data rate?

[1%]

Uhm... that is for youtube.

Youtube will take anything you throw at it and compress to whatever their rules are. Since overall bit rate of youtube is much much lower than any of those, they will all look the same.

After the 1st conversion its all down hill and you'll never get any quality back. That is why you want highest quality from the camera. Only exception might be intermediate codecs which expand the color space and make grading a little better.

Not everyone is shooting to deliver on youtube.

[he56ys5ysu7w4]

Another question reg bitrates.
Should I be concerned with the bitrate readings showing variable values that are much lower (35-45 mbps) than my set CBR 1.4 (that should give me +60mbps)?

Btw will we ever see bitrates like on the GH2 with the latest hack (176mbps)?

Looking forward to the clean HDMI out.

[John Kesl]

[/quote]
What is your sustained write speed? Regular mode. I have no problems with 2.0x even at high ISO. My write is 15-18MB/s

[/quote]

Hi, yeah. but. setting the camera to 2.0x doesn't mean it does that. according to my testing the highest I can set the camera and it actually means something bit rate wise is 1.8 on a good day. usually I leave it at 1.5x and let it ride. When I set my camera to 2.0 or more all it does is revert back to default, it 's not as if the camera stops recording, it just records at 1.0 default.

[1%]

The MVR resets are a bit hard to spot. The overlay blanks and then the bit rate goes back to "normalish" settings. When the buffer gets full it does something similar but can stop.

I've already seen 176 (and above, messing with D sizes). Actually written peaks? 267Mb/s on one of audio nut's graphs. Realistic average rates will probably stay around 100 until SD cards get faster.

Bit rate doesn't really "set" the rate... its just scaling I rate, P rate and the gop options. So you can get 17mbps at 3.0x depending on settings/scene/etc. We also need to get more out of the bit rate we already have.

[John Kesl]

The MVR resets are a bit hard to spot. The overlay blanks and then the bit rate goes back to "normalish" settings. When the buffer gets full it does something similar but can stop.

I've already seen 176 (and above, messing with D sizes). Actually written peaks? 267Mb/s on one of audio nut's graphs. Realistic average rates will probably stay around 100 until SD cards get faster.

Bit rate doesn't really "set" the rate... its just scaling I rate, P rate and the gop options. So you can get 17mbps at 3.0x depending on settings/scene/etc. We also need to get more out of the bit rate we already have.

Yup. It is very scene dependent. it seems the lower the light the higher the bit rate. I've been using Sandisk Extreme Pro SDHC 95Mb/s cards. And for me it seems that the highest, non buffer full reset is 1.8x without audio. Which when I analyze this in bits per sec I am getting 85-90 pretty steady and honestly for me that's plenty. 600mb per minute is quite a bit.