Nov 30, 2008

Encoding Via Your Editing Platform

If you've invested in a decent audio-editing or video-editing platform, chances are good that you'll use your editing platform to do your encoding. Most include a variety of export options. (You'll also want to export a broadcast-quality master for archival purposes, of course.) If your master includes lots of processing and complicated editing, you may want to render the broadcast-quality master and then encode using an encoding application or multi-format encoder, instead of doing all the processing twice. For most podcasts, exporting an encoded master directly from your timeline is probably easiest.

Most audio-editing platforms offer MP3 encoding. Many also offer encoding in a number of other formats:

  • Audacity (Windows, Mac, Linux): Offers MP3 and Ogg Vorbis export

  • Peak (Mac): Offers MP3 and AAC export

  • Garage Band (Mac): Offers AAC export, which is fine for iPods, but does not support MP3 export

  • Sound Forge (Windows): Offers a number of export options, including MP3, Ogg Vorbis, Windows Media, and RealAudio (see Figure 1)

    Figure 1: Sound Forge offers a large number of export options.

  • Audition (Windows): Also offers a wide variety of support, including MP3, Windows Media, and RealAudio

    Video-editing platforms also offer fairly rich export options:

  • Final Cut Pro (Mac): Offers QuickTime H.264 support

  • iMovie (Mac): Offers QuickTime H.264 support, including a preset for iPods

  • Adobe Premiere (PC): Offers Flash, QuickTime, Windows Media, and RealVideo support

  • Sony Vegas (PC): Offers QuickTime, Windows Media, and RealVideo support

  • Ulead Video Studio (PC): Offers QuickTime, Windows Media, and RealVideo support, and includes output templates for iPods and SmartPhones
  • Nov 23, 2008

    Making Format Choices | Podcast

    Because this is a technical manual that includes business advice concerning podcasting, you might expect that we would tell you which format is best for your podcast. Unfortunately, that's not something we can do. Things were much simpler when a podcast meant an MP3 file that was automatically downloaded to a desktop and transferred to an iPod. Now that the term podcasting has expanded to include a variety of portable media players and video, the podcasting format wars have begun.

    The territory that is being fought over is very valuable. As podcasting continues to grow in popularity and people continue to time-shift their media consumption habits, the large media conglomerates are scrambling to catch up to the thousands of already-successful podcast brands that have been established. Similarly, the portable media player manufacturers are fighting tooth and nail for control of the player market. Control the player, and you control access to the millions of people who are discovering podcasting.

    To some extent, we can learn from streaming media. The industry that RealNetworks pioneered quickly became a three-horse race when QuickTime and Windows Media entered the field. Flash was a late entry to the field and is making a dent in everyone's market share numbers. Experts have talked about the imminent demise of MPEG4 or RealNetworks, but the reality is that there seems to be room for all the streaming formats, and none of them is going away anytime soon.

    The same probably holds true for podcasting. The iPod has a massive share of the portable media player market, but with Microsoft coming out with a portable media player as this book is being written, that is sure to change. As the term podcasting has broadened, so has the way people listen to and watch podcasts. Studies have shown that half of all podcasts are actually watched on a desktop or laptop computer, not a portable media player.

    Because the podcasting industry is still in its infancy, the situation is likely to continue to change. There is no easy answer to the format question, nor one likely in the short term. However, in the interest of helping you make a decision, we can point out a few things to help you cut through the media hype:

  • If you're producing an audio podcast, MP3 gets you the widest compatibility.

  • If you're producing a video podcast, QuickTime is a good choice because it's compatible with the iPod and anyone who has iTunes installed.

  • If you don't care about portable media players and are offering video playback via your site, Flash is a good option because it has good cross-platform support.

  • Windows Media has better video quality than QuickTime and Flash, and there are a heck of a lot of PCs out there.

  • RealNetworks are making huge inroads into the mobile market, particularly in Europe.

    The best way to figure out what format is best for your podcast is to start off simple, possibly offering only a single stream option. Monitor your e-mail and your blog comments. After you've developed a bit of an audience, ask them what they prefer. Podcasting is still a relatively intimate broadcast medium, and the way to make loyal audience members is to give them what they want.
  • Nov 17, 2008

    Basic Encoding Techniques

    Whether you encode your podcast by exporting directly from your editing platform or by using a stand-alone encoder, you can specify a number of parameters. You may have only a few choices if you're using encoding presets, or you may have the opportunity to specify exactly how you want your podcast encoded.

    In the early days of low bit-rate encoding, back when people were connected to the Internet via slow modems, encoding technology was limited and required lots of tweaking to extract the best quality. Now, ten years later, codec technology and Internet connection speeds have improved so much that encoding high-quality podcasts should be within everyone's reach.

    This is particularly true of audio podcasts. Modern codecs such as RealAudio and Windows Media Audio are capable of attaining FM-mono quality at a mere 32 kbps. The MP3 codec lags behind in quality, but because you can safely encode your podcast at 128 kbps, you should not have any quality issues.

    Video is a little trickier. Assuming the majority of your audience is on a broadband connection, your video quality is limited by available bandwidth. Although you can't expect DVD quality at these bit rates, there's no reason why you can't create a perfectly acceptable video experience. This chapter helps you choose settings that should do the job. Let's start off with the easy stuff — audio encoding.

    Audio Encoding

    Audio encoding is easy, for a number of reasons. Raw audio files are large, but nowhere near as huge as video files. Therefore, the amount of compression that is needed to reduce them to a size that is suitable for Internet distribution is not excessive. Audio codec technology has progressed to a point where low bit rate encoding produces very good results. Podcasting reaps the benefits of ten years of cutthroat competition between RealNetworks and Microsoft, and the progress made by the MPEG organization with AAC encoding.

    Because modern codecs sound so good, you really don't need to do much tweaking when you're encoding audio. You really have to decide only three things: whether to encode in stereo or mono, whether to use a speech or a music codec, and what bit rate to use.

    Mono versus stereo
    The first thing to decide is whether to encode your podcast in stereo or mono. If your program is predominantly interviews or spoken word, encode in mono. Mono encodings are always higher fidelity at a given bit rate, because only a single channel is encoded instead of two. If you're encoding in mono, you can use a lower bit rate and get the same quality or you can get better quality than a stereo encoding at the same bit rate.

    If your content is predominantly music, you should encode in stereo, although it isn't strictly necessary. Even though music is recorded in stereo, most of the content is right in the center of the mix. The lead vocal, the snare drum, the bass drum, all will be right in the center of the speakers. And watch where you place your speakers. If you aren't sitting directly between the speakers, you aren't experiencing the full stereo effect anyway. However, one good reason to target stereo if you're playing music is that half your audience may be listening on headphones, which exaggerates the stereo effect.

    Speech versus music
    The next thing to decide is whether to use a speech codec or a music codec. If you're encoding an MP3 file, you don't have a choice. MP3 is a music codec. The good news is that MP3 is perfectly suitable as a speech codec as well, provided the bit rate is high enough.

    Speech codecs can take special shortcuts during the encoding process due to the nature of speech content. With speech, the dynamic range tends to be very limited, as is the frequency range. After you start talking, the chances are good that you'll continue to speak at roughly the same volume and in the same register. Knowing this, a speech codec can make intelligent decisions about how to encode the audio.

    Music content, on the other hand, has a wide dynamic and frequency range. There are bass drums and bass guitars, as well as crashing cymbals and violins. The shortcuts that a speech codec takes are completely unsuitable for encoding music content.

    So the choice is fairly obvious: If you're encoding content that is speech only, you can encode at very low bit rates and still achieve high quality using a speech codec. However, for most applications, a music codec is perfectly appropriate.

    Bit rates, sample rates, and quality equivalents
    The most important decision to make about your audio podcast encoding is what bit rate to use. The bit rate determines the eventual file size of your podcast, which in turn determines how long it takes to download. The bit rate also determines the fidelity of your podcast. The higher the bit rate, the higher fidelity your podcast is.

    The listed audio bit rates range from 20 kbps to 256 kbps. If you're producing audio-only podcasts, you should target somewhere between 64 kbps and 128 kbps. If you're encoding predominantly speech, you can safely stay at the low end of that; if you're encoding music, you may want to stick to the higher end of the spectrum.

    Note At the end of the day, you know best how you want the podcast to sound. Try encoding at a couple of different bit rates, and see which one sounds best to you.

    The other thing you may be able to set is the sampling rate. The sampling rate determines how much high-frequency information is encoded. For example, CD-quality audio uses a sample rate of 44.1 KHz, to capture the full 20–20,000 Hz frequency range. The sampling rate has to be at least double the highest frequency you're trying to capture. Depending on what bit rate you're targeting, you may be offered a few different sampling rates.

    The interesting thing about sampling rates is that a higher sampling rate isn't necessarily better. The sampling rate determines how often the incoming audio signal is sampled, so it determines how much audio the encoder has to try to encode. If you set a higher sampling rate, you're telling the encoder to try to encode more high-frequency information, but the encoder may have to sacrifice the overall quality of the encoding. Essentially, the sampling rate determines the trade-off between the frequency range and the fidelity of the encoding. At a given bit rate, an encoder can offer higher fidelity with a reduced frequency range or reduced fidelity with a higher frequency range.

    We suggest that you choose a lower sampling rate, thereby allowing the encoder to create a higher fidelity version of your podcast. There is very little information above 16 KHz in most audio programming, and most people don't have speakers that reproduce it faithfully anyway. Therefore, choosing a 32 KHz or 22 KHz sampling rate should provide more than enough high-frequency information.

    Nov 11, 2008

    Other Encoding Formats | Podcast

    MP3 is perfect for audio podcasts, but you may want to work in other formats for a number of reasons. Many portable media players now include color displays. Enhanced podcasts are appearing to take advantage of these color displays that include graphics along with the audio. Enhanced podcasts can also include links for people who are watching the podcast on a browser. Enhanced podcasts also feature chapters, so people can quickly skip to the next or previous section of your podcast.

    You can create enhanced podcasts using the QuickTime and Windows Media formats. Of course, enhanced QuickTime podcasts play back only on iPods or in iTunes, and enhanced Windows Media podcasts play back only in Windows Media player and Windows Media compatible portable media players. Another enhanced podcast format is the Audible format, which was developed for audio books. The Audible format includes the chapters feature, as well as the ability to store a bookmark, so that if you stop listening in the middle of a podcast, the next time you listen the podcast starts where you left off. Because the Audible format has been around for so long, it is widely supported by almost every portable media player, as well as in iTunes, Windows Media Player, and RealPlayer.

    If you're creating a video podcast, a number of different formats are available, including QuickTime, Windows Media, Real, and Flash. Video podcasts have the same compatibility issues as enhanced podcasts, which means limited compatibility across portable players, and they require that the appropriate player software is installed on the audience's computer.

    Caution People are weird. Talk to one person and he'll tell you why he would never install media player A on his machine, while the next person swears by player A and is convinced media player B is the devil's spawn. To some extent, these people split across platform lines (Mac users swear by QuickTime, Windows users Windows Media, and Flash users hate everything else), but not always. Each media format has its strengths and weaknesses. If you're planning on a video podcast, you should support at least two formats. Regardless of which formats you choose, plan on getting disgruntled e-mails and blog comments from crazed audience members. You can't please everyone.

    Another reason to consider alternative formats is if you want to protect your podcast files using Digital Rights Management (DRM). DRM lets you place restrictions on your podcast, for example letting only paid subscribers listen to it. Not all formats support DRM. Because most podcasts are free and most podcasters want as many listeners as they can get, very few podcasts use DRM. This may change as people begin charging for their podcasts.

    If you're going to offer your podcast in an alternative format, you may need to download and install encoding software (see Figure 1). Many of these formats will be included in your audio or video editing platforms, but if not, the software is generally available for free from the manufacturers.

  • QuickTime: iTunes will encode in the AAC and MP3 formats and exports videos to an iPod compatible format, but if you want to tinker with the encoding settings, get QuickTime Pro. You can upgrade any copy of QuickTime to the Pro version for a mere $29.

  • Windows Media: The Windows Media Encoder is available as a free download from the Microsoft site.

    Note Microsoft has recently dropped support for Windows Media encoding on the Mac. However, Mac users can encode in Windows Media using products from Flip4Mac:

  • Helix RealProducer: If you're considering the Real format, you need the RealProducer.

    Unfortunately, if you're targeting mobile phones (where the Real format is strongest), you need Helix Producer Mobile, which is incredibly expensive. If it's any consolation, you can download a trial version that's good for 30 days.

  • Flash: To encode into Shockwave Flash (.swf) or streaming flash (.flv), purchase the Flash authoring tool. Several multi-format encoders also offer Flash support. flashpro/

  • Audible: Audible doesn't make their encoding software publicly available. Instead, you have to upload your original MP3 file to their Wordcast service, and they do the encoding for you.

    Figure 1: The Windows Media Encoder is available for free from Microsoft for the PC platform (Mac users must use Flip4mac).
  • Nov 3, 2008

    MP3 Encoding Tools

    If you're producing an audio podcast, you're probably best producing it in the MP3 format. Although it isn't the best audio codec available, it is by far the most compatible and plays on virtually any computer or portable media device. It may not have all the bells and whistles of other formats, but your audience is far less likely to have technical issues, which means you'll get fewer negative comments on your blog.

    Virtually any editing platform you're working on should have built-in MP3 encoding capabilities, but on the off chance that it doesn't, a number of standalone MP3 encoding applications can get the job done; one such application is shown in Figure 1.

  • iTunes: iTunes isn't really an encoding application, but it converts audio files to mp3 on import if you choose to do so in your preferences.

  • LAME-based encoders: Despite the ironic origin of the name (Lame Ain't an MP3 Encoder), LAME is an open source MP3 encoding library that is used in almost all free MP3 encoding applications. There are probably hundreds of these available; google "MP3 encoder" and see for yourself.

    Figure 1: WinLAME is one of many free MP3 encoders available.