Syphon Recorder

The Syphon Recorder beta was released earlier this week. This is a new app in the Syphon family for OSX and it does exactly what it sounds like: it records video from any Syphon abled application and it also records sound from your source of choice.

So applications like VDMX that never had a recording function can now use Syphon Recorder to record the material straight to disk. I was doing tests using Soundflower to route music from Soundcloud playing in my browser into VDMX and recorded the whole session with Syphon Recorder without any hitches. And as an avid Modul8 user I’ve always been missing the option of recording sound with my visuals. In the next version of Modul8 that has Syphon support I will be able to use Syphon Recorder to record visuals and sound to disk.

But hold up… wait a minute. If you have ever used the Record to Disk function in Modul8, or just recorded any VJ session to disk in any VJ program , you know that it’s never a good idea to record to disk while reading video during a performance, it usually ends up with a lot of dropped frames and sad faces. So how are the Syphon guys handling this? I asked one of the creators, Tom “Bangnoise” Butterworth, how they handled this issue:

“We’ve worked hard to minimise the amount of work involved in recording, so you can get smooth video with the lowest possible impact on the rest of your system. Where possible, we use a custom shader to convert frames to 2vuy on the GPU, which halves the amount of data we have to move around and saves an expensive conversion stage during compression. We combine that with deferred-download of the data from the GPU and some careful threading and buffering to minimize the number of frames dropped due to system activity elsewhere.

During video playback you get constant spikes of disk activity while chunks of video are read – so if the disk is busy we accumulate frames until it’s ready to write again. Usually there is enough RAM available to easily handle this. We only drop frames if the data-rate of the compressed video is higher than your disk can keep up with – or if you are doing something involving heavy disk activity, such as performing a Time Machine backup or file-sharing, but hopefully you’re not doing either of those during performance.”

I just assume that faster processor, plenty of RAM, VRAM and fast disks like SSD would help this matter. Which of these things are most important, if any?

“Recording Apple Intermediate Codec onto an SSD, I can get ~60 FPS 1080 HD, but that’s with a fast processor and graphics card and with as little as possible else going on.

For the best performance, record to Apple Intermediate Codec, because it has a good balance of quality versus data-rate, and is fast to encode. For a lot of things you can get away with limiting the frame-rate to 30 FPS. A fast disk makes a big difference, especially for HD video. Never use a codec with alpha-channel support (Animation or “None”) if you don’t need the alpha-channel, as they slow every stage of recording down drastically.”

Edit: Syphon Recorder Beta 3 has been released. It restores audio recording on OSX 10.6.7 and adds support for ProRes codecs, etc.

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