Maritime/CaniTime, migrating from DV to HDMI MariTime/CaniTime today uses consumer video DV cameras transferring live video using Firewire (IEEE1394). As you probably all know, DV is no longer used on new consumer video cameras, and Firewire is getting scarce on consumer PC: s. So, the question arises: “Is there a suitable technical successor to DV/Firewire?” After considerable research and practical experiments I can today answer this question with “Yes, there is a successor!”. One cornerstone of MariTime/CaniTime has always been to use consumer electronics. So a new new solution must also use the same principle. What is the (possible) new technical solution? The solution will use: • Modern consumer HD video cameras • HDMI capture hardware • Partially re-written software •

HDMI As many readers are probably aware the HDMI interface is getting to be very common. • Modern TV: s and PC monitors have one or more HMDI input ports. • Modern PC: s have HDMI output ports built-in. • Most modern digital cameras have HDMI output ports • It seems that all consumer video cameras from makers like Sony/Canon/Panasonic et al have an HDMI output port, and this port will output live digital video which is what we need!

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PC HDMI input In the PC we need HDMI input. Lately there has appeared on the market several makes/models of HDMI capture hardware that can be added to a consumer PC to get HDMI input. (You can find examples of these if you search for “HDMI capture” on Google or Ebay) I have personally tested a number of these: The Timeleak HD72 is a plug-in card that uses a PC slot of type pci-e 1x . This slot type is found in almost all recent stationary PC:s. I use this in my development PC.

Illustration 1: Timeleak HD72 HDMI capture card

The Timeleak HD82 is a card that can be plugged into a laptop if it has an expresscard slot (N.B far from all laptops have these expansion slots!) I use this myself in a Dell Vostro laptop

Illustration 2: Timeleak HD82 HDMI capture card The Startech HDMI capture card is used by one early tester and seems to be working nicely! I have not tried it myself, but I have one on order.

Illustration 3: The Startech HDMI capture ExpressCard

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This is an external box that takes HDMI input and has USB3 output. Your PC does not need to have any extension slot. You do however need a PC with an integral USB3 port. I tried it with an USB external card in my development PC, but it gave me lots of problems (bluescreens etc.) My new motherboard with integral USB3 works better, but the unit still gives me somewhat erratic behaviour. I presently recommend that you stay away from these!

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PC specifications Using HDMI capture instead of DV capture means that the amount of data that has to be handled by the PC increases with at least one order of magnitude. This means that you will probably need to upgrade your present PC. As a rule-of-thumb I think the following will do fine: • • • • •

CPU: 2 GHz multi-core or better 4 Gb memory Available expansion slot for HDMI capture hardware or Integral USB3 port Operating system: 32- or 64 bit XP or newer

N.B! The manufacturers of HDMI capture hardware publish their own recommendations about the needed performance figures. These are often quite high. However, it is my understanding that these figures are based on the assumption that the user will use HDMI capture for real-time recording and full-frame compression. MariTime/CaniTime does not (normaly) use real-time full-frame compression.

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Some differences between DV/Firewire and HD/HDMI DV/Firewire

HD/HDMI

Maximum frame dimensions

720*576 (for PAL)

1920*1080

Max frame pixel count

414720

2073600

Effective bytes/frame

144000 (Chroma subsampling and compression)

4147200 (Chroma subsampling only) (2 bytes/pixel)

Megabytes/second (25 frames/second)

3.4

98.9

A consumer HD camera has a maximum pixel count of 1920*1080. However, some camera models can also be set to a lower bitcount e.g. 720*576. PAL models normally use 50i (i stands for interlace), meaning that the cameras will output 25 interlaced frames/second from which our software (using de-interlace) can extract 50 fields/second. Some camera models can also output something called 50p meaning 50 progressive (non-interlaced) frames/second. But, in effect 50i and 50p both give us the same timing resolution of 20 milliseconds (50 samples/second). Consumer HD video cameras store the recorded video on flash memory, and doing so it performs some very efficient compression (e.g. AVCHD). This is however of no significance to us, since we are only interested in the live video stream that the camera outputs through its HDMI port. And this video stream is (almost) uncompressed. The video is only subjected to something called “chroma sub-sampling” (4:2:2). The data amount flowing through HDMI is therefore reduced from 3 bytes/pixel(one byte for each colour RGB) to 2 bytes/pixel. And as you can see from the table above the data rate when capturing HD uncompressed video is almost 30 times higher than compressed DV. It probably goes without saying that this imposes significantly higher technical demands on the PC. However PC:s are getting cheaper and more powerful each year (Moore's law evidently still applies...) My tests tell me that a modern PC can actually cope well with the high data flow resulting from HDMI capture. (MariTime/CaniTime will compress the captured data when storing to disk, but this is a question outside the domain of this document)

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HD cameras In my actual testing of HDMI capture, I have been using a number of cameras. I bought two new of the cheapest models available at the time, namely. •

Sony HDR-CX220

•

Canon Legria HFR36

(The model numbers may actually be different in different markets) In summary, they both do the job nicely. Both cameras have plenty of optical zoom (especially at the telephoto end, where you need it). There is however one (or two) factor(s) that puts the Canon camera ahead. For our purpose we want to ensure that the camera uses a short shutter time. Higher-range video cameras often have the ability so set the shutter time specifically (e.g. 1/1000 second). Cheaper cameras (such as the ones mentioned above) have only a number of exposure modes. Sports mode is common, and this mode ensures a short (albeit unknown) exposure time. The Canon camera has a sports mode, but for unknown reasons the Sony camera does not offer it (it offers others modes such as landscape/fireworks/waterside). In actual use the auto mode seems to work fine giving a shutter time short enough, but I want to have somewhat better control over it... The Canon camera also came with an AC adapter included (something you really need). For the Sony it is an add-on option (it charges through USB)

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“Action cams” A type of camera with HDMI output that is becoming extremely popular these days is the “Action cam” (GoPro and many similar). These are not really useful for us since they have no optical zoom, and the fixed lens is very wide-angle.

HV10/HV20/HV30 One camera model that is a very good choice if you can find it (second hand since it is out of production) is the Canon HV20 (also HV10 and HV30 should do fine, but I have not tested them myself). The HV20 offers both DV/FireWire and HD/HDMI! So it has both firewire and HDMI output. It also has good controls for shutter time. This is what I use on my developmen setup.

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