Multiple bitrate streaming with IBM Video Streaming

When streaming to IBM Video Streaming, you can send either a single bitrate or multiple bitrate streams to your IBM Video Streaming channel ingest point.

What is video quality of experience (QoE)?

To engage and retain their audiences, Internet video broadcasters must deliver the best possible video Quality of Experience (QoE) to their viewers. An enjoyable video viewing experience is only obtained when the sharpest possible video quality is delivered continuously to the player without experiencing playback interruptions.

Studies show that despite high picture quality, viewers most typically abandon video sessions if frequent playback interruptions are experienced. Since high video quality is achieved with a combination of higher resolutions and frame rates, encoding higher quality video (e.g., HD) yields higher bitrates for a real-time data stream that must be delivered to the player on time.

Considering that network bandwidth fluctuates during a video session, a tradeoff between video quality and smooth playback must be made. High QoE streaming is always achieved by dynamically striking a balance between these factors.

In summary, to deliver engaging video QoE, smooth streaming is as important as video quality, presenting a tradeoff that must be adjusted dynamically during a video session.

Why are multiple bitrates important?

Having a multi-bitrate representation of the video content in each video session enables the use of Adaptive Bitrate (ABR) streaming technology to dynamically address the quality tradeoff and maximize viewer QoE during the video session.

ABR players constantly measure available network bandwidth and dynamically adjust video bitrate to match it. This is done by seamlessly switching among the video bitrates in the representation without interruptions.

The IBM Video Streaming player maximizes QoE by ensuring that viewers get the maximum video quality attainable at any moment with smooth playback while avoiding pauses or re-buffering events.

In a single bitrate scenario, viewers on fast connections can watch HD streams, while those on slower connections may experience buffering. A compromise is often made by sending a medium-quality stream, but this limits quality for faster connections and may still cause buffering for slower ones.

With multiple bitrate streaming, each viewer receives a stream optimized for their bandwidth:

• Fast connections: HD-quality stream
• Medium connections: Medium-quality stream
• Slow connections: Lower-quality stream without buffering

QoE is therefore maximized for each viewer at any given moment.

IBM Video Streaming Live Transcoding

While it is preferable to stream multiple bitrates from the source, doing so requires a powerful processor and sufficient bandwidth to encode and send multiple streams in parallel.

In many situations, processing power and bandwidth are limited, making this impractical. This is why the Transcoding service in IBM Video Streaming was developed.

IBM Video Streaming's Transcoding service provides the benefits of multi-bitrate streaming while requiring only a single stream ingest. You can send one high-resolution stream, and it will be re-encoded into multiple lower bitrate/resolution streams for viewers.

When utilizing IBM Live Transcoding, you send a single high-resolution stream that meets required encoding specifications, and it is re-encoded into the following streams:

Transcoding Output Specifications

Accessing Transcoding Settings

Log in to your account, then go to the Channel Settings tab for the channel you wish to enable. Choose Broadcast Settings, then Multi-quality Streaming Settings.

You will see a list of options that allow you to select which versions of your streams you want transcoded. Available options vary based on your plan and ingest stream quality.

Multiple Bitrates from External Encoders (Local Transcoding)

Some encoders allow you to send up to four bitrates directly from your encoder. These streams are passed through to the player as-is.

If you have sufficient processing power and bandwidth, this can serve as an alternative to IBM Video Streaming Live Transcoding.

When sending multiple bitrates with the same resolution, the player will display bitrate values instead of resolution. Refer to your encoder's documentation for configuration details.

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