The Problem with Transcontinental Podcasting

RSS HeadphonesI am not sure if anyone else has to manage audio files that have been .mp3 encoded prior to editing but for the podcast it has been causing some issues. This week however, I made a few changes to the encoding and it appears to have made a significant difference. Here is what I have done and if anyone has any further suggestions I would appreciate it.

The background of this whole saga is that I used to record the podcast using Hot Recorder. Since the release of Skype 3.0+ this has failed to record anything but silence. Although he website claims it does work with 3.0. So we had to look to an alternative. Knightwise has a Mac so that made it a lot easier for us to decide what to do but our decision then presented a few things we had to work around.

For some reason recording Skype on a Mac is relatively easy compared to a Windows based machine. Not sure why. It might be the way that Mac handles audio or that there has been more development on the Mac in this regard. So we decided to record the show on Knightwise’s Mac. He uses Call Recorder to record Skype, which by the way has excellent results. Far superior to what I was getting with Hot Recorder. But now we had a great recording of the show in .wav which is generally about 1GB in size… +2.4GB but it was on the other side of the world! We needed to get it to Oz in one piece and in good enough quality to work with.

A great supporter of the podcast donated a server which has excellent speed and storage in addition to as many FTP accounts as we needed. However sending a 1GB file across the world is out of the question, even zipped up it would be huge! The only answer that we could see was to encode the .wav as an .mp3 in as high a quality as possible. So Knightwise encodes the file raw as a 192 kbps, CD quality. The result is about 100MB, which is very manageable. He then sends the file to me via FTP.

I download the file and convert it to a .wav and edit the show as per usual. When finished the file would be encoded as an .mp3 at 64 kbps at 44100 khz. We dropped the bps a while back to give us a smaller file size, which we thought would be appreciated. However since we swapped to Knightwise recording the show the 64 bit quality has been giving us poor results. I have tried to optimize for quality in the encode but it has made no difference.

The problem is that .wav files loose certain frequencies when they are encoded to .mp3. You can’t get them back they are gone forever. Sure I do everything that I can to get the best results. But the 64 bit rate was stripping more of those frequencies out of the final file than I would like. This resulted in some rather strange sounding ambient sounds and hissing when there was talking in addition to making the music tracks terrible. There was only one thing for it.

This week I increased the bit rate. Although in the beginning the show was encoded at 96 kpbs; I thought I would take the intermediate step of 80 kpbs. The result was a file that was only about 4-5 MB larger but the pay off in quality I think was worth it.

The conclusion is that when we changed the way the show is recorded and then encoded before transfer, we should have decided to increase the bit rate. The 16 bit increase in quality has compensated for the lost frequencies the first time it was encoded as an .mp3 making the file resilient to being decoded to .wav and then back to a .mp3. A few further tweaks at the recording end will give us some further head room as far as quality.

I would remind all podcasters out there of one of the golden rules of editing, never edit a .mp3, always convert it to a .wav. I hope this hack helps anyone else faced with the same problem of transcontinental podcasting and file transfer. Check out this weeks show and compare the difference.

UPDATE: Hot Recorder has been updated to version 2.14, which I am told does work with Skype 3.0+. I am yet to test it but I will let you know the results. Thanks to mswiczar for the tip in the comments.

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Can I Change the Bit Rate of an Mp3?

I have seen this question come up a lot in the search terms that people use to get to Rooster’s Rail. So much so that I decided to answer the question here.

The short answer is no.

So I guess that deserves an explanation. Mp3 is an audio format that uses complicated compression formula that results in a much smaller file but retaining audio quality based upon what bit rate and sample rate was used to encode the file. Simply put:

Smaller file size = less quality

That is lower bit rate and sample rate.

Bigger file size = better quality

Higher bit rate and sample rate

Then there are mixes of the sample rate and bit rate that produces results that are in-between. There is also a file format called VBR or variable bit rate. I am not going to go into that here but that is basically where the bit rate varies according to the complexity of the music or audio file and results in a file size that can be smaller but retains a higher quality than an otherwise static bit-rate.

This bit rate and sample rate are dictated by the person that encodes the original file. The original file is often a .wav file wich is very large but of high quality. For example The Global Geek Podcast as a .wav file and goes for about one hour is over 500MB. Once encoded to an .mp3 file is between 20 and 25MB. I dictate the bit-rate and sample rate when I encode the file.

So lets say that you get that file which is encoded at 64bit and a sample rate of 44100khz. You want to lower the bit rate to make the file smaller. Sure you could using a program such as RazorLame, decode the file and then re-encode it at a lower bit rate such as 44bps (bit-rate). But the resultant quality would be lower than if I had used the original .wav file and encoded it at 44bps. This is because the best quality that you have is 64bps, that is as good as it gets. The quality can get no better than that. So in conjunction with the fact that .mp3 is a lossy file format and will get worse in quality every time it is opened and closed or encoded you end up with pretty much crap.

Same can be said if you wanted to go up in quality and therefore bit-rate. If you had a file that was encoded at 64bps there is no way on earth to make it better quality than what it is. If anything going up in bit-rate will make it worse because it will very successfully highlight the imperfections that are a result of encoding something as an .mp3 file. When a file is compressed in this way it decreases in quality regardless of the bit-rate. It all has to do with the fact that to make it a smaller file you have to ditch some of the data that the original file contains. That said it would take a very good ear to detect the imperfections in a high bit-rate encoded audio file, but it is there.

Moral of the story is that if you have an .mp3 file leave it as it is. Unless you can get the original source file there is no way to increase or decrease the quality and maintain any sort of standard about the quality of it. I hope this clears up a bit of confusion that there appears to be out there.
I tried to think of a good analogy to use for this post and could not, but this is the lame one that I did come up with:

Trying to change the bit rate of an .mp3 file is like baking a cake and then deciding that you want to know how to make it so it has less sugar in it than what you originally put in it and still have the cake!

What Bit Rate for Podcasts?

I really, honestly do not know the answer to this question. What is the best bit rate to encode a podcast at? Also does that answer depend upon the fact that you are a listener or a podcaster or hosting service?

I do the post production work for the Global Geek Podcast. Before moving to TPN I always encoded the podcast at 44khz and 96kbps. That works out at about 35 – 40MB per show (depending on length between 40 minutes to an hour). We have what I think is great audio quality, but am I spoiling ourselves and our listeners and potentially excluding others?

We have never had a complaint about the file size of the show. No-one has ever said it was too big. People have commented on the quality and said it is great and we have worked hard to get it that way. But I now question if that is over kill. So I tried to figure out what bit rate is the most common. I did a very small survey of the podcasts I have on the computer. I only have nine on it at the moment – most of them are on the MP3 Player (where they should be).

Anyway I got the following breakdown:

Total of 9 Podcasts:

  • 2 encoded at 96kbps
  • 4 encoded at 64kbps
  • 3 encoded at 48kbps

A conclusive survey that does not make. But maybe I am aiming too high. What quality do listeners expect of a podcast? Do they want a small file and lower quality so that they get the content without the bandwidth. Or do they want great quality and a larger file size? With the size of MP3 players now the storage is not an issue I don’t think. But I know in Australia the cost of bandwidth might be. The cost of faster connections is expensive and so many users are on a maximum of 256/64 or 512/128. So does a larger file size deter them from listening to our show? Could we have a bigger audience if we made it smaller and if that is the case what size is acceptable?

With the uptake of broadband technology there is a step towards encoding at a larger bit rate but what should it be? Perhaps 64kbps is a good place. I listen to quite a few podcasts that are recorded at 64kbps and they sound good. A one hour podcast encoded at 64kbps is about 28MB (voice only). Is this a big difference to 96kbps? Well it is between 10 and 15 MB. Will that mean the difference between more listeners and a balance between keeping your existing ones because of what they expect? Will you loose listeners by lowering the bit rate dramatically and will it matter because of the number you pick up. To me it does anyway, I care that we keep the listeners we have.

The other big consideration here is the hosting cost. I know that I had to go to the plan one up from the basic plan in order to have the podcast encoded at such a high bit rate. So that privilege cost me $10US/month instead of $5US/month. That was a cost that I thought was worth it. Also what if your podcast is being hosted by a network, what file size is reasonable for them to host? Is it acceptable that you have a higher bit rate than the other shows that are hosted there and is it necessary? Personally, I would like to find a happy medium between file size, bit rate and quality. I want the best quality at a reasonable file size. I don’t want my hosting provider to get pissed off that the show is too large. In addition to that fact; the network wants as many people to listen to as many shows as possible. If it is possible that people are “turned off” by a large file size, then that is not for the benefit of the network and I would not do it. In that instance the file size should be smaller at the sacrifice of quality for the benefit of the network and I need to accept that.

As a listener I do not care what size a file is. I have a fast Internet connection and it really does not bother me. I like high quality podcasts but I listen to some that are not of a high quality as far as bit rate because the content is good. So is good quality a cover for shit content? If it is; it is not sustainable long term. So as a listener of podcasts I don’t search for podcasts based on audio quality or file size, and maybe I have just answered my question in part.

Having made these points I will say that some basic editing will improve quality out of sight. I have turned off podcasts because they have not bothered to do this basic editing. They were unlistenable and total shit and they should have thought the same! I wonder if some podcasters even listen to it after they have recorded it. So what do I mean by “basic editing?”

Basic editing in my opinion is:

  • Setting levels before you start, especially if you are recording Skype using a software application. This means setting your levels with enough “headroom” to get loud during a podcast so that you don’t “clip” the recording. And not so soft that you have to amplify it dramatically to get something to work with.
  • Don’t edit the podcast as an MP3, MP3 is a “lossy” format and gets worse and worse in quality every time you re-encode it or open it and save it.
  • Run a compressor on the audio to “smooth” the audio. That is take out the high’s and bring up the lows.
  • Run the compressor a few more times.
  • Normalise” the audio, basically set the zero level. Makes the podcast the same volume and means that the listener isn’t constantly turning their volume up and down.
  • You may need to “amplify” the whole audio after using the compressor and normalising the audio. You don’t want the listener running out of volume because it is too soft!
  • Any added or imported audio needs the above steps.

Believe it or not the above takes the least amount of time in my editing but makes the biggest difference. I do go a step further and edit the actual audio and take out the umms and errs and we always stuff things up and say well we will edit that out. The time is also in the transitions and the mixing of the imported audio, making it all work together (the best that I can). So maybe you can see why as a podcaster I want it to sound as good as I can, I put a lot of effort into both the pre and post production. But is that at the neglect of other issues? Is this basic and advanced editing enough to make it a “quality” podcast?

Please leave a comment and tell me what you think. Tell me if you are a listener or a podcaster. Podcasters, tell me what you encode your podcast at and why. Listeners please answer my questions for me. As I said at the start of this post I really do not know what the right answer is, that’s why I have posed lots of questions. It would be great to get some answers, although I am not sure there is one.

Updated the Webpage

Nothing major today, I have made a few changes to the Global Geek Podcast Homepage.

Because the web-page for the Global Geek Podcast was such hard work I have avoided changing anything for fear it would all be ruined. But I can say that now it is all set and basically the way it will be for a while, editing it in a minor way was easy. I just cut and paste the HTML our and into Nvu which is an open source WYSIWYG editor for web pages. It is excellent because as you would know from the podcast Sebastian and I do not try to pass ourselves off as HTML guru’s at all. Quite the opposite; we suck! Nvu is highly recommended by myself, especially if you don’t want to spend any money – it works!

As you might know from Sebastian’s blog, he purchased a domain name: sebrt.com for his blog page, which he has “masked” with that domain. So I thought it only fair that the link to his blog be that, so that done he should now be happy.

The other change is that you will notice that there is a link to The Knightsite. There is a bit of a story behind this one. Another great story of networking, Skype and the community of podcasters, bloggers. Turns out that this Belgian dude called Joe (a.k.a Knightwise) was cruising around the Skype “search for contacts” option in Skype. I don’t know what for but eh, he was there. He happened across Sebastian’s Skype id which detailed his podcasting involvement. So Joe called him up, as it happens Sebastian and I were talking at the time and we invited the Knight into the conversation and we all hit it off. Joe is a top bloke and he has a podcast called the Knightcast. It is a great quality podcast; hell he uses VBR encoding at high bit rates – bandwidth must be cheap in Belgum! Plus I think his accent is cool.

The KnightcastSo Knightwise should have a place on our Podcast Homepage. We often talk now and encourage each other with our projects and we are planning some joint ones coming up so that will be fun. It is true that the internet does not know borders or nationality. I am stoked that I have yet another person added to my own community that is mutually moving towards bettering our “space”. There is no way in the world that my own universe would have opened up as much as it has without this wonderful medium called the internet, which is starting to reflect real world interactions and ways of meeting new friends. And that is just plain cool.

By the way please have a listen to the Knightcast, great quality and very impressive editing, he deserves a bigger audience and he is a top bloke.

So that’s about it for the web-page update, but as usual I can talk about anything for too long!