Month: July 2007

A quick article about how to record a remote interview and how to fix the audio levels after the interview.

I got a few questions about the equipment I used to record the podcast interview with Tony yesterday. I recorded it remotely using Skype – Tony was in West Seattle and I’m in Sammamish. We were both wearing headsets which I recommend because even though Skype is good at cutting out feedback from a PC speaker, some noise does get through if you’re not wearing a headset.

I used Pamela to record the audio. I recommend the Pro version because the other versions limit your recording to 30 minutes or less. Pamela is free for the first 30 days and it’s about $12 after that. A tip when using Pamela: To get to the mp3 audio files, right-click on a recording and click “open call recording folder”. It took me a while to figure that out.

The only complaint I have about Pamela is that it doesn’t regulate the volume of the caller vs. the callee. So my voice was very loud and Tony’s was much softer. It’s taking the audio directly from Skype, so perhaps that’s too much to ask. I also haven’t experimented playing around with the Skype audio settings. Fixing this was time consuming:

I used Audacity, and open source sound editor to fix the difference in Audio volume, and besides the actual interview, this occupied most of my time putting the podcast together. Using Audacity you can see the waveform and it’s quite clear where the audio level is much lower. So I selected the parts in the audio where Tony speaks and applied the Amplify effect. Amplify automatically detects the largest waveform and sets the amplification so that the largest waveform won’t clip – in other words it wont over-amplify and cause distortion. I recommend using the default number it gives you and if that’s too low, then look at the area of the clip you’ve selected and you’ll probably see a spike in the waveform that’s causing amplify to give you a low amplification number. Just select around that spike and you’ll be able to boost the signal more.

I’m sure there’s an easier way to do this, but I tried using Leveller and a couple of other tools and the results weren’t as good as Amplify.

Next time, I’m going to make darn sure my levels are much lower and as close as possible to the person I’m calling. Pamela has a level indicator when you’re recording, so I might try and use that as a visual guide and tweak Skype’s audio settings.

Once I’d finished working with the clip in Audacity, I saved it as a WAV file rather than using Audacity’s ‘save-as mp3’ option and I used RazorLame to convert the WAV to mp3. That gave me more control over the mp3 quality. Under Edit/LAME options, select 24kbit as the bitrate and ‘mono’ as the mode.

Then I just uploaded the file to my blog server and presto!

I logged onto my blog this morning and it wouldn’t load. I tried to ping the server and it was still up. Then I tried ssh’ing into the server and it connected. I hit reload again in my browser and starting mumbling WTF.

Then I ran ‘uptime’ on the server and got something like this:

09:52:40 up 325 days, 6:45, 2 users, load average: 0.28, 0.28, 0.27

That’s a little high, so I checked how many apache processes there were and it was at MaxClients, apache was working pretty hard. I checked my Analytics stats and by 7am today I had already done as much traffic as yesterday:

So I tailed the web server log file and it just flew off the screen.

I figured out Reddit was the source. Someone posted a blog entry I wrote yesterday about Rescuetime and it’s getting a few votes.

I run a standard WordPress.org install (newest version). My server has 1G of RAM and is an AMD Athlon XP 2100. It’s on a 10 Megabit backbone, so has plenty of bandwidth. So I made some basic changes to the server.

Apache needed to handle more concurrent connections, and I had MaxClients set to 15. But the server was using too much memory for me to increase maxclients, and MySQL was the memory hog. So changed the mysql config to use less memory because fetching blog entries from disk is not that much hard work.

My my.cnf file (the config file for mysql) has the following settings now:

key_buffer = 50M
sort_buffer_size = 5M
read_buffer_size = 1M
read_rnd_buffer_size = 1M
myisam_sort_buffer_size = 5M
query_cache_size = 4M
That’s a fairly small number of the key buffer and the other caches are very low too, but I’m just serving around 300 blog entries, so I could probably do away with the key buffer completely and just rely on disk access and it would still be ok. I left the query cache at 4M in the hope that it would save me some disk access when fetching blog entries.

I changed Apache’s config from this:

MinSpareServers 15
MaxSpareServers 15
StartServers 15
MaxClients 30

to this:

MinSpareServers 15
MaxSpareServers 45
StartServers 30
MaxClients 60

It fixed it immediately and my blog is now blazingly fast. 🙂 Right now apache has 49 children, so it’s still getting a lot of traffic, but it’s not hitting MaxClients which means it’s not turning away users.