Videos are a great asset to a webcast – especially if they are interesting and pertinent to your content. It breaks up the presentation, and allows your speakers a little break as well. However, if you are going to incorporate videos into your webcast, there are a few key technical items you should consider first.
You want to make sure that the videos are in the best file format recommended by the webcasting platform that you are using. We typically recommend an .mp4, it’s a pretty universal format on most platforms from WebEx to ON24. You also want to make sure that the files size and bitrate of the video are small enough to play and be consumed by your attendees without causing issues. The best way to do this is to look at the bitrate of your file and compress it down to as small as possible without impacting the quality of the video. What exactly is the bitrate you ask? You’ve probably heard the term but let’s break it down to the different “pieces.”
Bitrate
In all video files, you have the video data, audio data, and “Overhead Container” which has the data about the video and the codec type – these are basically the instructions that a computer would use to play the file. The Bitrate is the number of “bits per second” (bps) at which data in a video is being delivered. The size of the file and the quality of the image and sound are both controlled by the bit rate used. The higher the bit rate, the better the potential quality and the larger the file size. Lower bit rates should be used for international audience or events with a large number of people accessing the webcast from the same network. Higher overall bit rates may be utilized, but when exceeding 800 Kbps, many attendees may experience latency, buffering or playback issues.
Frame Rate
If you are looking at the details of a file, you will also notice a Frame Per second rate or (fps). For low movement videos, such as instructional videos and live webcams, a 15fps frame rate will provide a clear and quality stream to the audience. Higher frame rates are permissible but do consider that 24+ fps is utilized for HD video and broadcast television; 15 fps will greatly reduce the file size without noticeably affecting quality. If a cursor is the only constant motion, 1 fps may be sufficient.
Frame Size
For most webinar platforms, video clips are displayed in the slide viewing area, so to keep things consistent, we recommend matching the video frame size to the same aspect ratio as your slides. So if you are using slides that are 16:9 (widescreen), you would ideally want your video to be 16:9. If your slides are 4:3, then your video frame should also be 4:3 so it fits in the space without being stretched or resized. Dimensions for videos – for 16:9 ratio you would want 640 x 360, 480 x 270 and 320 x 180. For 4:3, you would want 640 x 480, 440 x 330, 400 x 300 and 320 x240 pixels.
Audio Format and Specs
AAC Audio format is preferred if using H.264, with MP3 the mobile stream might encounter issues. 32 Kbps audio is sufficient and will allow the video to be encoded at a higher bit rate. Anything over 96 Kbps for the mono audio stream is superfluous unless the audio was recorded in a studio.
So next time you are creating a video for your webinar or webcast, keep the specifications and tips above in mind to ensure your video will shine without the risk of streaming issues for your attendees. V2 is happy to assist with any file compression or clean up needed to ensure your videos play flawlessly.