Saturday, 17 September 2016

Live TV interviews (Using DSLR with Skype on a Mac)

I have done quite a lot of live TV interviews on BBC, Sky News, and RT (Russia Today). If you want me to do a TV interview on anything Internet related contact the AAISP press office.

The first interview was with Sky News, and was in a studio. I had a few days notice. It was all very scary and new, but one can get used to anything. These days it is much more relaxed. RT tend to give a couple of hours notice.

Interviews with BBC were also in a studio. I have been in three different studios now. When RT called for an interview, with only a few hours notice, they suggested a studio, but then said "or we could use Skype". Well, I am not a Skype user, but a choice of install Skype or spend all evening travelling to and from a stupid for 3 minutes on air - I chose Skype.

It was pretty simple - install Skype, wait for a "call", and live TV interview.
  • I used the apple headphones as they avoid any issue with feedback or noise cancelling.
    • The mic is not that good, but was OK - probably better than the one in the screen/Mac.
    • Later interviews I had grown a beard and so the mic would make a scraping noise, not good
  • I used the in build camera in my Mac
    • It claims to be HD - I am not sure of the spec, could just be 720, and does not look that good
    • It is a tiny camera, so never going to be brilliant
    • It points at an odd angle, so I either had to tilt up the Mac (which showed all my ceiling lights behind me) to lower my chair stupidly low. I chose the latter.
After many RT interviews like this, for the latest (a couple of days ago) I thought I would try something better. We have some good audio/video kit now at work, and so I plugged in the Zoom H4n Pro via USB. It is obviously much better quality than the inbuilt mic or the headphone mic. When you connect USB it prompts for mass storage or audio, and so I picked the latter - as if by magic I now have H4 as a new audio input (and output) on my Mac, and Skype can see that.

Whilst waiting for the call on Skype I googled a bit to see if I could use the Canon DSLR camera as a web cam. I found a solution, which was very clunky, but worked. I have since seen some other s/w that supposedly works more directly with the camera, but not tried that.

The process is pretty simple though...
  • Install CamTwist
    • This creates a new web cam that can be used as video input on the Mac
    • It actually does (in this case) screen grab of the desktop - you pick a rectangle
    • Beware - it has settings for the web cam size that default to something tiny - you go in to a menu to set those (I picked 1920x1080) and restarted it and the apps using it
  • Run the EOS utility for "live view" on Mac screen
  • Point the CamTwist virtual webcam input window to the EOS live view window
    • This means a 4k video camera displayed on a scaled window on a small part of a 5k Mac screen, captured and called to present to be a 1920x1080 webcam. Messy, or what.
    • Be careful no other windows pop up over the live view at all as they will appear!
This is the end result (this was recorded using a camera pointed at a TV so is not that good).

As you can see, the video is not that bad, but something horrible has happened with the audio! I sound a lot more Micky Mouse than usual and I seem to be stuttering!

From what we can tell, when I plugged in the H4n it offered 44.1kHz or 48kHz. I just picked the default (44.1kHz). I can only assume something (maybe Skype) assumed it was 48kHz, and so processed the audio as higher pitched, but then kept running out of audio and so repeated a fraction of a second hence making me stutter.

So, I am trying to do better! I ordered a Blackmagic design Ultra Studio Mini Recorder which does HDMI or SDI to Thunderbolt. This is not that expensive but it is important to realise that it does not do HDCP so cannot capture from Sky, etc. It is find for a DSLR that has HDMI output though. It is worth getting a thunderbolt cable too and I had to get a mini HDMI to full HDMI cable to work with the camera.

This is not the end of the fun and games though.

First off, getting the camera to play ball...
  • I had to set the HDMI mode not to overlay the usual focus and settings controls. There is a menu for that.
  • The HDMI out is 1080, and can be 1080p or 1080i. I set 1080p (why not) and 50 fps.
  • The recording is separate. I did have set to 4k 25fps, but obviously that means some processing to get to the HDMI, and seemed to add a video lag compared to sound (even using cameras own mic). I changed to match HDMI 1080p/50fps. Seems better.
  • You still need the EOS utility to set live view - this allows you to lock the camera so it is actually mirror up and feeding video without timing out. Just setting video mode and not recoding soon stops. I could have recorded as well I guess. May be a nice idea next interview.
  • I may have to find a mains power adapter for camera to ensure the battery does not catch me out. Thankfully interviews are short, but sound/video checks first and so on can take time.
  • The EOS live view lets me play with focus and stuff as well, which is fun, so live I can change focus to another person - would be good if we had two people interviews and a camera operator.
So, with the camera working, I turn my attention back to audio. My plan was to either use the H4n via USB as before (but 48kHz this time) or use audio line out in to camera external mic. The idea of the latter is it means audio / video via HDMI so should avoid A/V sync issues.

Turns out A/V sync issues are a nightmare!
  • To start with, I was not sure how to test - I FaceTimed my son - he said sync was shit and audio like a second behind video.
  • Eventually I decided simpler to record using Photo Booth and play back to check.
  • I found audio ahead of video slightly in most cases, even when audio is direct in to external mic. I think I have managed to improve that a lot by changing video record mode to match the HDMI settings to minimise any processing being done.
  • It seems that actually the H4n on USB works just as well as via line out to camera, so USB will get better quality direct in to audio devices.
  • Unfortunately, at one point, I managed to create the huge lag with audio behind, but not quite work out how. So clearly, testing is needed before I go live.
I need a longer thunderbolt cable, and a USB extension lead. I am still using the Apple headphones for the audio output (talkback so I can hear interviewer). But I think I am ready for my next interview now - and I know to check my A/V sync before I start this time!


  1. In my experience you can avoid a lot of headaches if you can manage to embed the audio to the video signal before it hits the computer. Matching and predicting latency for different signal paths in a computer with different drivers and hardware interfaces is incredibly difficult. Unfortunately DSLR's often are not easy to manage with external audio and I'm not sure if there are good HDMI audio embedders out there. Most DSLR's treat the HDMI output as merely a preview mechanism. I do video over IP transmission / link monitoring gigs for live TV sometimes and I try to stay with SDI and professional gear just to avoid these issues. (Though even the cheapest HD-SDI cameras are a thousand bucks).

    I definitely recommend 48 kHz with the Ultrastudio and all videostuff in general. A lot of software and hardware kind of expects it and may get confused if something different is used. Also it is a good idea to connect a video feed to the thunderbolt adapter before starting any application that ingests the video. I have had nasty issues where the Blackmagic driver thought the embedded audio was 44.1k instead of 48k just because it did not have a live feed connected at first.

  2. (Typing this out again, who on Earth puts a 'Sign out' button where one might expect a submit button to be!)

    I agree with the above commenter that you should try to embed audio upstream of capture with your BlackMagic device. In theory (drivers being in order), the audio should stay in sync, the problem you will find with consumer applications is that the drivers that provide core audio functionality aren't very good (software such as XSplit which can talk a little more 'natively' to the box don't tend to have such problems).

    You need to be very aware of any options that allow you to listen to yourself or cancel echo/noise as these can cause delay.

    Even with 48k you may well suffer issues as the clocks on the sound card and the video capture card are free-running and will not be PPM correct unless you can sync them with word clock (which you cannot). Therefore one sample of audio doesn't always fit into one frame of video (or rather, the clock generating the audio stream attached to the video isn't the same as the sound card) and you can get some weird glitches going on, this is jitter.

    If you don't want to purchase a camera with balanced audio inputs (such as a Canon XF105), you could look at a condenser-style microphone (Beyerdynamic MCE85s are good), preamp and embedder box.

    1. I think the bad sync we say may have been face time as we managed to see it even using internal mic and even external mic in the canon and so taking audio over HDMI. I tried FaceTime with this yesterday and audio was way out using Mac internal mic and camera, but telling FaceTime to change audio to another source (the H4) fixed it, in call. At least I know I have to watch out for it. We'll see on next interview.

  3. A couple of 'optics' comments if I may. I've watched a few interviews on RT and a couple of visual mistakes people often make is setting the camera too low (or less often too high) - it should be just below eyeline IMO, and secondly paying insufficient attention to the background - you want to shoot for completely neutral, or vaguely related to your status as 'expert'.

    1. The up/down and size is very much dictated by the TV channel - telling me where they want me in relation to graphics over lay and how they will crop and so on.

      The background, well, with using my Mac built in camera which is chained to the desk (literally) gave few options but obviously a proper camera on a tripod with a choice of lenses gives more scope within my office. I don't (currently) have blank walls, but maybe I should make one. However, it was amusing to have the bar behind me. Using large aperture helps as whatever background can be blurred to be less distracting. Sometimes just being in a hi-tech office as a background can be a good choice for the sort of talks I do.

      My son had two of his bedroom walls painted green screen so maybe I should do a shot up there and find some keying s/w for the Mac, then I can be anywhere :-)