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Saturday, September 23 2017 @ 02:26 AM CDT

Local Archive

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The video the rest of the world will see from your camera is likely to be far lower quality than what the camera actually captures. Chances are that you will want to capture this higher resolution video (and audio) for use later for such things as DVDs and, as in the case of Hancock Wildlife Foundation, for education and research purposes.

As there are two different types of camera setups – IP and composite video – there are two different ways of capturing the live video at full resolution:

  • split the composite video to a second encoder – and capture that video to disk
  • pull a second stream from the IP camera at full resolution, and store that video to disk

To the right you see the bundle of cables and splitters used initially at the Hornby Island site


Split the Signal

In multi-camera and microphone situations I've done some fancy footwork with cables to enhance the multiple streams and introduce some redundancy into things. In a situation with two cameras and two microphones, the two microphones can be cross-patched to the two streams to introduce "stereo" sound; not really stereo, but sound from both microphones such that there may be "depth" for some sounds but there will also be potential to catch some sounds that make the video stream experience better for both cameras.

This dual-encoding of sound gets around one major flaw in today's live-streaming environment; watching two streams at the same time, you'll more than likely notice quite a time-lag between them, introduced by the stream re-sending systems depending on the load on them. If one camera has more viewers, it may lag behind the other camera by several seconds at times. This does not make listening to two sound tracks very useful.

Splitting the video (and audio) from a composite video signal source and audio source is as easy as placing a “Y” connector on the cable and running the resulting two outputs to two different but otherwise identical computers. 

It is even possible to split the video more than once and connect one output to a monitor TV directly so you can watch it – but... beware of splitting it too many times as each time will lower the signal and may result in added noise or lowered resolution. We use a video amplifier with multi-outputs in cases like this.

In extreme situations, you may need to split the signals more than just once or twice. In this case you should look into purchasing a video/audio amplifier like the one pictured here. This unit takes in video and stereo audio, and puts out 4 amplified streams. This particular unit was purchased for use in a situation where the single camera was to power the encoder, a local archive system, the site owner's TV, and a separate DVD burner. Note that the unit also has the added advantage of S-video in/out, meaning it could take a S-video in and put out both composite and S-video, or vice-versa.

Re-Encoding for Archive

Using a second encoder to archive locally to disk is the best way to get long-term archival video and sound from your camera. Trying to grab the stream remotely is far less than optimal for a couple of reasons, not the least of which is that the actual video and sound are far lower quality than what you can get locally.

You can also grab your archives in a completely different format from the transmitted streams.

Note that the format (codec and transport stream definitions) should be one that you are comfortable with and able to work with after the fact. These do not need to be the same as used for the live stream, and in fact probably should be “lossless” in nature (MJPEG for example) or at least MPEG2 or high-quality AVI. You may be limited by your archive software, but no matter, set it to the highest quality it can deal with.

The second/archive encoder can be set up with either the same (typically Adobe’s Flash Media Encoder) software, but set to save to disk, or to completely different software (such as Pinnacle’s capture section of their software package)

Disk space used to be the determining factor for such archives, however with Terabyte drives less than $100 “raw” these days, and the ability to use something like the USB/E-SATA external drive bay from Thermaltake to house them, this should not be an issue.

We tend to use Linux as our archive system since it allows completely unattended capture of the high-resolution video in any of many  different formats. It also has easy scripting to do things like grab 10 minute time-slices, give them file names including date-time, and file them away in date-oriented folders for easy access at a later time. This is far from easy with PC-based capture technologies.

Before you commit to long-term use of an archive scenario you should test it from end to end. Encode a few hours, then take what is encoded and import it into your editing/rendering software to do some editing. Ensure that what you get out when you’ve done the editing is what you expect. I’ve had occasion to have to re-encode video captured because the end-user simply didn’t have software that could use the MPEG2 input, they required AVI. Re-encoding a couple of hours of video is not a big thing. Re-encoding several months of video is! I know, I’ve done it.

The Second Encoder

Note that I say two different encoders. It is possible to put two video capture cards into a PC, but I have had problems running them both under Windows and using two different programs at the same time. I’m not saying it is impossible – in fact I’ve done it successfully with a couple of combinations – but you should experiment before you decide that’s the way you’re going to do things because there are many potential problem areas, not the least of which is simply having a powerful enough computer to do both tasks.

Second IP Stream Capture

IP cameras today will allow, and can handle, multiple streams from their one video source. Some I’ve seen will allow up to 50 people to watch at once. The real limitation is the network from the camera to the destination(s) as well as the encoder settings for the streams. Higher resolution requires more network bandwidth, so 50 streams at 2 Megabits/second will saturate a 100 Mbps connection. Needless to say, if your connection to the camera is wireless it’s not likely to have 100 Mbps throughput, many max out at about 5Mbps for long-duration sessions.

Pulling a second “full data rate” stream such as MJPEG (as opposed to another H.264 stream) may stress some home WiFi networks, depending on other uses and interference from nearby systems on the same channel. The new “802.11-N” systems should have more than enough bandwidth, but in some instances we’ve fallen back on 802.11-A (5 GHz) “backhaul” wireless systems that have a design throughput of 20Mbps.

Once you have the second stream available, your method of archiving it can be any of several different systems, including the software that the camera manufacturer provides.

As noted above, we prefer a Linux system with some custom but fairly mundane software for doing raw archives. The files are in 10 minute chunks with the date/time/source as part of the file name.

Another option is something like Zoneminder – the open source security monitoring software. It can be set up not only to do 100% archives, but also to do partial and motion-detected archives separately (if your computer is fast enough) so that highlights are available. See the section on Production for more details.

Whatever archive facility you choose, do test it from time to time to ensure you can retrieve the results into your favourite editing software. We've noted long-term problems with some mixes of hardware/software that didn't show up until after the first few days.

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