Bitrate increasing

[Bachi]

Hey there,

some time ago I purchased a new SD card to be able to use bitrate increasing in ML.
It's a SanDisk Extreme 16GB class 10 with 45MB/s. But when I wanted to increase the Bitrate to about x1.4, it already stops recording automatically. So do I have a wrong card again? Please help :/

[RMAlpine]

Yeah, I'm afraid so
That card still doesn't have a fast enough write speed to be stable enough to shoot higher bit rates.
In fact, I have that same memory card and even sometimes in standard 1.0x CBR (the Canon default setting) it stops recording because the card is not fast enough.
One thing you can do though to shoot short bursts of higher bit rate video is to disable your audio. I am able to record all the way up to 3.0x at times for a minute or two with the audio disabled. But that being said, you could just use an external recorder to capture even better quality audio anyway and then just sync that track up to your video in post.

But back to your memory card problem. You'd need a faster card. This might be overkill but this is what I'm saving up for.

http://www.google.com/products/catalog?q=sandisk+95mb/s&hl=en&prmd=imvns&bav=on.2,or.r_gc.r_pw.r_qf.&biw=1278&bih=664&um=1&ie=UTF-8&tbm=shop&cid=3213910149492026989&sa=X&ei=JS1AUKvUEM3BiwLZ8IGYDQ&ved=0CJABEOUNMAI#ps-sellers

Sand Disc Extreme Pro 95 MB/s

It's just about double the card we have now so it should definitely help with that problem. Still havent gotten one myself though, so not certain.

[mrak1979]

Which camera are you guys using?

[Roman]

It still seems unclear to me as to whether there's any point in getting a 95mb/s card, as your camera needs to put the card into UHS-I mode to run at that speed - which only a 650D can do as best I can tell, which doesnt have magic lantern available for it yet.

One thing to try that seems to help though, turn off the magic lantern overlays, so its a clear view on the display, and turn off the audio.

I've been able to record at (up to) 1.8x the bitrate with no stops doing it that way.

[Zaphod]

@RMAlpine, I use an Extreme III too, the older Class 6 one and the new class 10 one. My 550D records video perfectly every single time (at standard 1.0x CBR) even on the noisiest and busiest scenes, so there must be a problem on your card. SanDisk cards are pretty consistent.

For both you and @Bachi, do a "Low Level" format of your SD card. It does a true format and clears all the data blocks completely (a normal format only tells the card to overwrite the data blocks on next write). See if that works.

[Bachi]

Yeah, I'm afraid so
That card still doesn't have a fast enough write speed to be stable enough to shoot higher bit rates.
In fact, I have that same memory card and even sometimes in standard 1.0x CBR (the Canon default setting) it stops recording because the card is not fast enough.
One thing you can do though to shoot short bursts of higher bit rate video is to disable your audio. I am able to record all the way up to 3.0x at times for a minute or two with the audio disabled. But that being said, you could just use an external recorder to capture even better quality audio anyway and then just sync that track up to your video in post.

But back to your memory card problem. You'd need a faster card. This might be overkill but this is what I'm saving up for.

http://www.google.com/products/catalog?q=sandisk+95mb/s&hl=en&prmd=imvns&bav=on.2,or.r_gc.r_pw.r_qf.&biw=1278&bih=664&um=1&ie=UTF-8&tbm=shop&cid=3213910149492026989&sa=X&ei=JS1AUKvUEM3BiwLZ8IGYDQ&ved=0CJABEOUNMAI#ps-sellers

Sand Disc Extreme Pro 95 MB/s

It's just about double the card we have now so it should definitely help with that problem. Still havent gotten one myself though, so not certain.

aah this is annoying... We got these two cards sponsored a while ago just to find out they're not the right ones...but thanks for your answer Indeed, without sound x3.0 is possible. I do record interviews with an external recorder, but random scenes with an external rec device are a bit too much time consuming for me to sync...

[Roman]

I dont think its fair to assume that the SD card is the bottleneck, given the symptoms.

If with sound, it can record at say 1.4x max, and without sound it can record at say 2x or 3x max depending on camera...

If the SD card write speed was the bottleneck, wouldnt the sound have to be taking up that remaining difference between 1.4x and 3x?

Which isnt possible given that the total allocation for sound is probably 10% or less of the standard bit rate to start with, and (as best I know) the sound portion isnt increased in size when you up the bit rate.

Looking at each file in bitrate graph viewer program for what the peaks are (with and without sound) would tell you whether or not you'd be wasting your money on flasher SD cards.

I've managed to happily record at 1.8x with sound turned off, with $11 8gig class 10 Apacer SD cards.

Also, have a read about UHS-I:

http://www.integralmemory.com/faq/what-uhs-1

Most notably the part about the host device needing to be UHS-I compliant to run at the full speed, which your camera likely isnt unless its a 650D.

[JasonATL]

I've found the bit rate multiplier use to depend on a number of factors, of roughly the same importance:
1. Sound on/off
2. Speed of SD or CF card
3. ISO
4. Light (daylight/indoor)
5. Action within the frame

For this reason, I think you likely will become frustrated if you think that there are any clear rules as to when a specific a multiplier will always work. For example, using a Sandisk Extreme 45 MB/s SD card: I have reliably recorded at 2.4x on my 600D in most daylight, at low ISO (100 or 160), with sound off; I have reliably recorded at 2.0x indoors, low key, at low ISO, with sound on; I have reliably recorded at 3.0x indoors, low key, low ISO, with sound off... But, I have also had recording stop in almost all of those situations at some point.

I also had a 5D Mark II for a weekend and used a Lexar UDMA 7 1000 MB/s card. While I didn't test it nearly as much as the 600D, I had about the same experiences, except that it did stop on me at 2.3x in bright sunlight.

Here's a link to a test I just posted if anyone is interested to see the benefits of the CBR multiplier:

[1%]

You get different rates even at the same x number because the CBR function mainly sets the slice quality via the quantizer (qscale) and then actual br is decided from that. Thats why CBR isn't really CBR it just tries to lower quantizer when the br starts rising past all of those numbers.

Complex scenes like static, trees, rain will fill the buffer instantly like the h264e can't compress at that quality fast enough. If you get a faster card you clear that buffer sooner and can handle more complex scenes to a point.

Sustained write of the card at whatever regular mode before UHS-1 is what matters. Just so happens UHS-1 cards are faster in regular modes too. Other cards will work, don't look at peak write speeds.

[Roman]

Thanks for the input, 1%.

I'd like to quantify some results with various cards on a 600D.

I remember reading something about an SD card speed tester function for a previous version of ML, can that be downloaded anywhere still?

[1%]

I see write speed in kbps in the dm log. You can probably look up sustained write for your card online or test in a computer.