Skype podcasting revisited

My podcasts are almost invariably recordings of phone calls. Following the advice of my audio guru, Doug Kaye, I’m using a Telos ONE to achieve decent audio quality using POTS (plain old telephone service). But from time to time I revisit the question of whether Internet calling, using Skype or another voice-over-IP solution, can produce results of equal (or better) quality.

The good news, since the last time I tried this, is that it’s easier to record Skype calls. The recipes used to involve a whole lot of baling wire and black magic. But now there are Skype add-ins that simplify things quite a bit.

For today’s test I used two different products: MX Skype Recorder for Windows, and the Ecamm Call Recorder for the Mac. Because friends and family now refuse my requests to involve them in audio recording experiments — and who can blame them? — I manned both ends of a Skype call, shuttling between a PC in one room (with an analog headset) and a Mac in the other (with a USB headset).

Doug Kaye’s recipe for using the Telos ONE involves splitting the caller and callee onto separate channels of a stereo recording. That enables the kind of editing I illustrated in this brief screencast. I’m happy to report that both of these Skype recorders enable the same kind of thing. MX Skype Recorder will directly produce a split-channel WAV file. The Ecamm Call Recorder produces a QuickTime movie with two stereo tracks, one for each half of the call, but you can extract them and recombine the parts to achieve the same result.

So that’s all good. But when I finished my test call and reviewed both recordings, I found in both cases that while the quality was fine for the local voice, it was sketchy for the remote voice. In particular, listening to the recordings made from each end of the call, I hear the occasional dropouts and compression artifacts that I always hear in every Internet call, whether it’s on Vonage or Skype or iChat or Windows Messenger.

Just for kicks, I took the two recordings apart, swapped channels, and put them back together to create two new versions of the test call. One combines both local voices and it sounds like this. The other combines both remote voices and it sounds like this.

I’ll be recording a podcast tomorrow and, since it’ll be an international call, I’d like to be able to use voice-over-IP. Based on these results, though, my conclusion is that combining two locally-made recordings — one of which the interview will upload and I will download after the call — will yield the best outcome.

In this case my interviewee is willing to play along, so we’ll give it a shot and see how it goes. In general, of course, that isn’t something you can expect an interviewee to do. But I don’t see a workable alternative. Skype-based podcasting still doesn’t feel like a first class option. Am I missing something?

23 Comments

  1. “there’s a number of USB Mics like the Samson C01U that are under $100 and work fantastic”

    I’ll look into one of those. But the mic won’t improve the network, and that’s the source of the trouble I’m hearing.

  2. > Am I missing something?

    That, with Ecamm at least, you can record Skype video. As a consumer I might trade voice quality against voice+image – even lo-res image.

  3. I’m quite pleased with the results I’m seeing with Ecamm; it definitely beats the previous approach, which involved me having to be in the office, plugged into POTS via an Edirol recorder.

    Skype from my end, with a Plantronics headset (DSP 400), achieves good results to a Skype recipient at the other end (cf this call with Nova Spivack of Radar Networks). It’s also not bad via SkypeOut to a phone line at the other end (cf this call with Eric Miller, formerly of W3C and now at Zepheira).

    Both calls were trans-Atlantic.

  4. John, Leo Laporte has been using Skype for interviews for some time. The very best quality interviews that he does are for his Security Now netcast with Steve Gibson. For those calls I think both Leo and Steve forward certain ports through their firewall to their client machines to improve quality. Search the following transcript for “skype”

    http://www.grc.com/sn/SN-003.txt

    It does not intuitively make sense to me why Skype would have breakdowns inside your house. I don’t know, however, what type of Kabuki port dance Skype is doing when you connect from one machine to another behind a firewall. Does the traffic go out and then back in?

    -JD

  5. This has been bugging me so I did a little research.

    Skype has a reasonably good network admin guide: http://www.skype.com/security/guide-for-network-admins.pdf

    From reading that, I suspect that the two machines behind your firewall are actually traversing outside the firewall and connecting back through a relay. Below is an excerpt from page 4 of the admin document (page 10 of the PDF):

    As shown in Step 1 of Figure 1-1, when two Skype users wish to communicate with one another, the caller fi rst simply tries to contact the called party directly. However, if the called party is protected by a firewall, then the called party’s computer is asked by the Global Index to connect in the reverse direction back to the caller’s computer, as shown in Step 2 of Figure 1-1. If either of these connections succeeds, then the call is established using a direct connection, providing the most reliable and lowest-latency connection possible between the two parties.However, if both parties to the call are behind restrictive firewalls, then neither party will be able to reach the other directly. This requires the call to be relayed by a third parties who are reachable by both parties to the call. To do this, a small number of Skype users are selected as relay hosts by the Global Index.

    I think to get the call quality you want, you need to ensure that the machines are directly connecting. Looks like its time to review ye ol’ ipchains rules.

    -JD

  6. “I think to get the call quality you want, you need to ensure that the machines are directly connecting.”

    Excellent point, thanks. I had been thinking that would mostly be a nonstarter because it would be necessary to open up both ends, and I couldn’t necessarily expect the other person to do that. But apparently opening up just my end will suffice, so I’ll give that a try.

    In other news, I wound up using Jajah to broker a call between the US and Canada today, which I recorded for a podcast. It’s a clever service! POTS on both ends is convenient. The sound quality wasn’t great on the recording, so I’ll still be using an out-of-band recording from the remote end, but the interview pointed out that he was calling from a 2.4GHz cordless phone that’s competing with a flock of WiFi networks so it might not have been a fair test.

  7. w.r.t. Jajah recording: how did you do the recording? I may start using Jajah for conference calls. It looks cheaper than some other options.

    I’ve been wanting to do a series of interviews and looking for an easy solution that does not require my subject to be a techno-geek.

    -j

  8. Jon: I’ve used the recording feature in GrandCentral (www.grandcentral.com), and it works quite well. Potentially POTS on both ends, but you can also use Gizmo (www.gizmoproject.com) as a pure VOIP endpoint. I find GrandCentral to be a quite amazing service in general, in fact…and they even have New Hampshire numbers available, Jon!

    Gizmo (SIP VOIP) also has recording built-in, but I’ve never tried it. I’m happy to work as a guinea pig if you’re interested, though!

  9. I think you can get better results than with POTS for the most part.

    This vcast gives a step by step on setting up a router for Skype so you and your interviewee can exchange packets directly

  10. Jon: I use the Pamela plugin (www.pamela-systems.com) for Skype which does the stereo thing and get good results. Skype can be a bit erratic on call quality but generally this is pretty good.

  11. Geoff, thanks for the labrats link. That’s good stuff and I was having some trouble finding something so straight forward.

    -JD

  12. Hi,

    I am looking for reviews of “USB, Headset mics”. Of particular interest is the sound quality of these things when they are being used to record for podcasting (not over skype but “in studio”).

    If you or any of your readers could offer a link to such a review it would be enormously helpful,
    Thanks.

    JustaJ0e

  13. To further lend credence to the Skype direct connection that Leo Laporte pulls off on a weekly basis, multiple times…

    http://www.twit.tv/ww

    Leo does the Windows Weekly podcast with Paul Thurotte. Paul is in the Boston metro area if I’m not mistaken. Leo is in Petaluma, CA. Paul always sounds good, with very occasionally some artifacts thrown in, but otherwise it sounds just as if Paul recorded himself and (in a ‘double-ender’) and sent the file to Leo. But I know that’s not the case. Similarly, Leo’s hosts on Skype where possible try to use the same brand and model of mic that Leo uses. In the case of Steve Gibson and the Security Now podcast they’re matched, one to one (Heil PR-40’s on both ends) and the quality is as good as if Steve and Leo were in the same room.

  14. Getting the mix-minus setup for this can be “fun”.
    Rob Walch at PodCast411 has supplied the following setup on Skype/Skype-out interviews:

    http://www.podcast411.com/mixer.pdf

    This way, his setup is the same whether or not the remote end in using a phone or a PC and a high quality microphone. The use of a stand-alone recorder insures that PC resources are free for Skype to use, and also eliminates the noise associated with recording directly on the computer (using the consumer audio devices).

  15. We just released a new tool for podcasting on Skype. http://www.callgraph.in supports wav file encoding and 2 channel recording for easier editing. We also offer services like online storage, sharing, search and transcriptiong. Pls. do check it out.

  16. Try my free MP3 Skype Recorder It automatically starts recording and saves to mp3 file, with chosen mode (mono,stereo) and bitrate. Easy and effective tool for Skype recording in less then one click.

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