Understanding playback quality problems

With so many variables in the process of creating streaming video, from the characteristics of your source video to the software you use and the settings you choose, there are plenty of reasons why the quality of the end product might fall short your goal. Here are a few common problems, and some recommendations that might improve the viewing experience.

Streaming Flash video too blurry or pixelated during movement

Assuming the source video does not exhibit this problem, this can happen for several reasons during the exporting process:

1. Adobe/Macromedia's Flash Exporter performs poorly when exporting from uncompressed AVI files and possibly from other large source formats due to its lack of 2-pass encoding. Try exporting to a format such as QuickTime or Windows Media for a similar delivery rate, then using that file as the source for your FLV export.
   
2. Using double-pass encoding (available in 3rd party software such as Flix and Sorenson Squeeze) will always result in video with less artifacts than single-pass encoding.

Streaming Flash video is too dark

The Flash 7 codec is noted for video that is somewhat darker than the source. Try adjusting the video characteristics of your source prior to exporting to compensate.

Sound too loud or soft

This problem is almost certainly a problem with your source file. Use video editing software such as Final Cut or Adobe Premiere to adjust the volume prior to exporting.

Audio and video are out of sync

This is a common problem for many video formats. Try the following:

1. Determine whether the video is out of sync in your source video. If not, experimenting with the output settings might yield better results.
   
   
2. Determine whether the audio and video are out of sync by the same amount from beginning to end, or whether the gap is greater near the end of the video. If the gap is consistant, you can probably shift the audio track slightly in your source file to compensate.
   

Video skips during playback

• This is usually the result of the user's connection speed not matching the intended delivery rate. For instance, if you choose export settings for delivering the stream at a rate of 400 Kbps, a small percentage of residential DSL or cable broadband users will experience this problem (more so if their ISP is experiencing heavy network usage). Dial-up users will likely find that the video is unplayable.
  
  
• This problem can also occur when an anomoly in your export settings results in a file size that is simply too large to be streamed at your intended rate. Use the following formula to measure an approximate target size for your exported video:
  

  Delivery rate in Kbps X minutes X .0075 = file size in MB

  
  (Note: KbPS is kilobits per second, not kilobytes per second)
  
  For example, a one-hour of video for delivery at 400 kilobits per second should be approximately 180 MB:
  

  400 Kbps X 60 minutes X .0075 = 180 MB

  In our experience, FLV files end up being about 10% - 15% larger than the results of this formula without signifacant adverse effects. A small amount of this discrepency is metadata that is not streamed. Additionally, the delivery rate varies during streaming, and user's connection speeds also vary. This allows some video data to be transmitted in advance and stored in buffer when the user's connection speed exceeds the delivery rate.