If available, have the videographer provide you with a set of headphones so you can listen directly from the microphone feed. You will be surprised at how much better you will be able to hear. The only drawback to the headphones is not knowing which direction the voice came from if there are many attorneys in the room. This is very important when it comes to video synchronization, as many times transcripts are sent out to be synchronized after the fact. It could be months or even years after the deposition is taken.
Attorneys highlight the transcript for splicing purposes.
If something is said on the video that they may not want to hear, that comment or testimony is highlighted so that the videographer can splice out that section. A videotaped deposition was recently played to a jury in an Illinois court. The attorneys waived the reporting by the official reporter of this videotaped testimony as it was playing to the jury since the judge had the transcript. Unfortunately, the judge noticed many inaccuracies and missing testimony compared to the videotape. During this same trial, three different videos were played, all with the same results.