Feb 28, 2009

RSS: Podcasting's Secret Sauce

The RSS file really is the secret behind podcasting. RSS is an acronym for Really Simple Syndication.

In the late 1990s, during the first Internet "boom," companies such as Marimba, PointCast, and DataChannel offered news distribution based on a technology known as "push." Push technology delivered information to client PCs when the server was ready to push the content. This turned out to be technologically impractical because the server tried to push the information out all at once, which consumed huge amounts of bandwidth and clogged personal and corporate networks.

A new model called "poll then pull" evolved. In this model, the server did not send out updated information until it was asked for by individual clients. RSS, inspired by the various content syndication formats used in push technology, was originally proposed by Dave Winer in 1997 while he was running a company called Userland. RSS was designed to enable a particular form of news syndication known today as blogging. Other companies such as Netscape and Microsoft developed versions of their own known as RDF and CDF.

Winer attempted to work with Netscape and Microsoft until Netscape abandoned the effort in 1999, and in late 2000 Userland released version 0.92 of the standard. Optional elements including the crucial tag were added in 2002, and RSS was eventually standardized in its current form in July 2003. Several versions of the RSS story exist; you can read them at these sites:


As interesting as the RSS story is, all you really need to know at this point is that your RSS feed is a critical ingredient in the success of your podcast. It's the mechanism by which folks subscribe to and automatically receive your new episodes.

Feb 24, 2009

Adding a Logo to an MP3 Podcast

If you're at all serious about podcasting, you're going to want a logo. Adding a logo gives your podcast that extra bit of polish and recognition. And after you have a logo, you should embed it in every podcast you produce. However, it takes a few additional steps. Embedding images in MP3 files is a relatively recent phenomenon.

The original MP3 file specification did not include a way to attach metadata, such as the title, author, or copyright information. It wasn't until 1996 and the introduction of ID3 tags that metadata could be included in MP3 files. The original ID3 specification was fairly simple, including fields for title, album, year, genre, and comment. Over the years, the ID3 specification has grown to include much more, such as the track number on a CD, the composer, lyrics, and most important to this discussion, an embedded image, designed to contain album cover art. You can use this ability to embed a logo into your podcasts.

To add a logo to your podcast, you have to use an ID3 tag editor. Many are available, as a quick Internet search will reveal. As luck would have it, you probably already have one installed: iTunes. All you have to do is import your MP3-encoded podcast into iTunes and edit the ID3 tags via the Info window:

  1. Open iTunes, and import your podcast by choosing Import from the File menu.

  2. Find your podcast. If you're in library mode, you can sort by Date Added. This brings your podcast to the top of the list if you're in descending order.

  3. Highlight your podcast, and choose Get Info from the File menu. This opens the Info window.


    If you're not seeing the Artwork tab, then your podcast isn't yet in a format that supports embedded artwork, for example an unencoded WAV file. This is why it's a twostep process: First encode your file to MP3, and then open it and add your logo.

  4. Click the Artwork tab, and then click the Add button to browse for your logo graphic.

  5. Select your logo graphic, and click the Open button. You should see your graphic displayed in the Info window. Your graphic can be in BMP, GIF, JPG, or PNG format and any size up to 300×300 pixels. You should make sure that it looks good at different resolutions, because it will be displayed at different sizes on different players. iTunes provides a handy slider bar that lets you preview what your logo looks like at various resolutions. If it doesn't look good when it is scaled, you should consider revising it until it does.


    The 300 × 300 image size is not a strict limitation. However, using a larger resolution is not recommended because it may not be supported on portable media players, and it adds unnecessary payload to your podcast file.

  6. Click the OK button to save your changes.

Your logo is now embedded in your MP3 file and will be displayed in iTunes, Windows Media Player, and on portable media player screens that display graphics.

Feb 2, 2009

Encoding H.264 video using QuickTime Pro

You can export H.264 vide from QuickTime Pro in a number of ways. The simplest way is to use the iPod preset. This is perfect for creating iPod compatible files, but it gives you no control over any of the settings. You may want to tweak the settings a bit to suit your podcast, in which case you'll have to create your own encoding setting.

Using the iPod preset

Using the iPod preset is simple:

1. Open QuickTime Pro, and open the video to be encoded.

2. Choose Export from the File menu. This opens the Export window, shown in Figure 1

Figure 1: Export an iPod compatible video from QuickTime Pro using this preset.

3. From the drop-down menu, choose Movie to iPod (320×240).

4. Click Save. QuickTime Pro exports an iPod compatible H.264 video.

The only problem with using this preset is that it doesn't give you any control over any of the encoding options. You can't select a bit rate, a resolution, or anything else. Of course, it's guaranteed to work on an iPod, which is pretty handy. But the default bit rate is rather high, clocking in at over 800 kbps. This is fine for a short podcast, but if your podcast is longer than, say, 5 minutes, you're looking at a pretty serious download. You may want to dial the bit rate down to reduce the file size. To do this, you have to set your encoding settings by hand.

Encoding using custom H.264 settings

QuickTime also makes it easy to customize the encoding settings. There are a few more steps than using the iPod preset, but you have far more control over the output. Follow these steps:

1. Open QuickTime Pro, and open the video to be encoded.

2. Choose Export from the File menu. Again, this opens the Export window, as shown in Figure 2.

Figure 2: Here's how to get to the MPEG-4 video export settings.

3. Choose Movie to MPEG-4 from the Export drop-down menu.

4. Click the Options button to get to the video export settings. To begin with, this opens the MPEG-4 video settings, as shown in Figure 3.

Figure 3: Configure QuickTime MPEG-4 export video settings with this dialog box.

5. Select MP4 from the File Format drop-down menu.

Note QuickTime Pro defaults to MP4 (ISMA) for MPEG-4 output. ISMA stands for the Internet Streaming Media Alliance. Unfortunately the H.264 codec is not yet considered ISMA compliant (as of Fall 2006). This really doesn't mean anything. The H.264 codec is part of the MPEG-4 standard and will play back in any modern QuickTime player or iPod. For best quality, you should choose the MP4 option, not MP4(ISMA), so you can use the H.264 codec.

6. Choose H.264 from the Video Format drop-down menu.

7. Enter a bit rate for your file. Remember that the total bit rate is the video bit rate plus the audio bit rate.

8. Enter your screen resolution in the Image Size field. If you want iPod compatible files, choose 320×240.

9. Click the Video Options button to access the advanced encoding options. This opens the Advanced Video Settings window, shown in Figure 4.

Figure 4: Be sure to select Multi-pass encoding for the highest-quality results.

10. Choose Best Quality (Multi-pass) encoding mode, and click OK.

Note You may be wondering about the profiles restriction (Main versus Baseline) on this screen. In MPEG-4 encoding profiles define the "tools" that can be used to encode the video. Consequently these profiles also define the tools required to play back the encoded video. In this example, the Main profile provides more encoding tools than the Base profile. Since our goal is the highest quality video, we chose the Main profile.

The MPEG-4 standard is incredibly broad and frankly, not written in a way that a layman can understand. For a fantastic, concise, and fun-to-read explanation of the MPEG-4 standard, we recommend Damian Stolarz' Mastering Internet Video.

11. Now it's time to configure the settings for your audio. Select Audio from the second dropdown menu in the MPEG-4 Export Settings window. This changes the information displayed in the bottom half of the window from video settings to audio settings, as shown in Figure 5.

Figure 5: Configuring QuickTime MPEG-4 export audio settings

12. The first thing to choose is the audio codec you want to use from the Audio Format dropdown menu. In fact, the only codec offered for MPEG-4 encoding is AAC, which is just fine, because it offers great quality.

13. Next, select the desired bit rate from the Data Rate drop-down menu. A rate of 32 kbps should provide good quality.

14. If you're encoding spoken word content or want slightly higher fidelity, choose mono from the Channels drop-down menu.

15. The next available setting is the Output Sample Rate. This determines how much highfrequency information is contained in the final encoding. In general, the default setting works just fine. However, you can experiment with lowering the setting to get increased fidelity.

16. Finally, set your Encoding Quality to Best. This makes the encoding process take a little longer, but hey, your podcast is worth it.

17. Click OK to return to the Export menu, and then click Save to start the export/encoding process. You'll see the QuickTime Export progress window, shown in Figure 6, which gives you an idea how long the process will take. Depending on the length of your podcast, you may have time to grab a cup of coffee.

Figure 6: The QuickTime export progress window lets you know how long it's going to take.