Our transcoding system maintains the aspect ratio of the source video using the width and scaling the height accordingly.
If a device, such as a phone or tablet, does not support an encode’s resolution, the video will not play. This is usually not an issue for desktops and laptops, but can be an issue for phones and tablets.
When a bit rate is specified for an encoding, the actual bit rate is not consistent during playback. Variable bit rate (VBR) stores more data for the portions of videos that have a high level of change between frames (e.g., action scenes) and less data for portions that have little change. As a result, the bit rate will vary during playback, but the average will be the bit rate you specify.
Ooyala uses a two-pass encoding method o optimize performance and video quality. The first pass analyzes the content to determine the bitrate for each part of the video. The second pass encodes the video based on the analysis.
To prevent excessive switching between encodings, we recommend making sure that each encoding of the adaptive bitrate (ABR) profile is at least 300Kbps (kilobits per second) apart (e.g., 300, 600, 900, and 1200 instead of 300, 450, 600, and 750).
The audio bit rate is the number of bits in one second of audio. The higher the audio bit rate, the higher the quality, and viewers’ bandwidth requirements. You can select any audio bit rate of up to 156kb/s. For example:
- 32Kbps (kilobits per second)—AM Radio Quality
- 64Kbps—Voice Quality
- 96Kbps—FM Radio Quality
- 128Kbps—Standard Quality (recommended)
If possible, we recommend that all encodings use the same audio bit rate. Otherwise, some viewers might notice the audio level change as the player switches encodings.
The following are just a few of the variables that can affect a viewer's playback experience:
The CPU and GPU abilities of the device; other programs running in the background
The viewer's device and screen size
The connection speed or bandwidth cap
Latency caused by the wireless router, such as the distance from the router and local congestion
Latency caused by network traffic between the device and server hosting the video
Viewer's browser brand, version, and available plugins (e.g., Flash, Silverlight, and so on)
For smooth playback, viewer bandwidth should be around double the video playback bitrate (audio plus video bitrates).