Preface: Quick-Start Guide to Common Problems
This book is a hands-on guide to real-world compression. A lot of you are perhaps browsing it right now trying to find a quick solution to a pressing problem. Here are some answers.
My Boss Says I Need to Put Some Video on Our Web Site. Where do I Start?
For simple video on a web page, embedding Flash (Chapter 15) or Silverlight (Chapter 27) is the easiest mechanism today. And generally a web server is fine for delivering short content (see next question).
Do I Need a Streaming Server to Put Video on the Web?
Generally, no, for shorter clips of a single bitrate. It’s only long-form content (more than 15 minutes) or when high-quality real-time playback is needed that you’ll need a streaming server. For longer content, or to deliver the best quality for uses with a broad range of connection speeds, technologies like IIS Smooth Streaming or Flash’s Dynamic Streaming can work well.
My Video has Horizontal Lines Wherever there is Motion
Your video source is interlaced, where even and odd lines contain images from slightly different times, and it wasn’t converted to a normal progressive format.
• See page 26 in Chapter 2 for a description of interlacing
• See pages 112–115 in Chapter 6 for how to deinterlace.
If you’re shooting your own content, you should be shooting progressive, not interlaced.
My DVD is All Flashing and Stroby Whenever There’s Motion
Your source is interlaced like described in the previous answer. You encoded your DVD using the wrong field order, so what should have been the first field displayed is now the second field.
This topic is covered in Chapter 9 on page 179.
My Video Looks Terrible and Blocky
You’re probably suffering from some combination of one or more of the following:
• Too big a frame size (see pages 120–121 in Chapter 6).
• Too low a data rate (see page 141 in Chapter 7).
• Sub-optimal encoding settings (see chapter for your format or codec).
My Video is All Stretched or Squished
Your video was probably produced in 4:3 or 16:9 aspect ratio, and then encoded at a different aspect ratio. This is typically addressed by telling your compression tool what shape your source is, and specifying the right frame size for output. See page 120 in Chapter 6 for how to correct.
My Video has Annoying Black Bars in it
Your video has letterboxing (top and bottom) or pillarboxing (left and right). Either the input and output aspect ratios don’t match, or there are black bars in the source.
If your source doesn’t have the black bars, see the previous question for where to learn about correcting for aspect ratio.
If your source has black bars, you’ll need to crop them out before encoding the video.
There’s this Annoying Flashing Line at the Top of My Video
That’s probably “Line 21,” which in analog video specifies a video space set aside for closed captioning.
My Audio is Way Too Quiet
Your audio is probably way too quiet. Most compression tools have a “Normalize” filter that raises the volume of quiet audio while leaving already loud enough audio alone. See “Normalization” on pages 136–137 in Chapter 6.
My Audio Sounds Terrible
You are probably using too low a data rate. Good audio doesn’t take up that many bits with modern codecs, so even if your video quality is limited by bandwidth, your audio should never be distractingly bad. See page 66 in Chapter 4 on how to balance video and audio bitrates.
Where Can I Host My Video?
There’s no shortage of ways to host a video:
• If you have access to a web server (which you do if you have a web site), you can use that for progressive download media.
• If you don’t care about doing your own compression or having another brand on your video, you can use a service like YouTube or Soapbox that will take an uploaded file, compress it, and host it.
• If your organization has an account with a content distribution network (CDN) like Akamai, Limelight, Level 3, or CDNetworks, use that.
• If you don’t have needs big enough for a CDN but want to control your compression and brand, there are new lower-cost services like Sorenson 360 that start at $99/month.
How do I make my video come out with the right size file after compression?
If you have a particular file size you want to target, you just need to multiply the total data rate of video and audio by the duration of the clip. However, data rates are typically measured in kilobits per second, while file size is measured in megabytes. To calculate between them:
So if you have 30 minutes of 500 Kbps video, you’d get:
Users Don’t Have the Right Player to See My Content
First, find out what players your users have access to. If the video will be played back on a web site, most servers will allow you to log what plug-ins and versions are installed on the browsers that come to your site. It’s also helpful to track what operating systems visitors are running.
What players are available depends on the market you’re addressing and how you’re delivering your video. Good choices include the following:
• Flash: Chapter 15
• Silverlight: Chapter 27
• Windows Media Player (default for Windows users): Chapter 16
• QuickTime (default for Mac users): Chapter 29
How do I Pick the Right Video Format(s)?
The right format depends on the player and version of that player you’re targeting. You may need to target more than one player, which means you may need to compress in more than one format.
My Users Keep Getting “Buffering” Errors or Pauses in Playback
This happens when your users aren’t able to get your video at the data rate it’s encoded at. For generic web video, you probably want to stick to a data rate of 800 Kbps or lower if all users will share a single data rate. Remember, that data rate is based on video and audio—make sure that you’re not accidentally leaving the audio bitrate too high.
Adaptive streaming techniques like Smooth Streaming and Dyamic Streaming can offer a much better experience here, because they customize the delivery bitrate on the fly based upon each user’s connection speed.