The easiest way to conceptualize Media- Melon QBR is as a server-side, per-title delivery mechanism. That is, whereas per-title encoding analyzes your video file before encoding to determine the optimal bitrate ladder,
QBR analyzes the stream after encoding but before delivery. Then, QBR delivers segments at
“the optimal visual quality,” rather than at the
highest bandwidth conditions would currently support.
MediaMelon claims QBR reduces bandwidth costs and buffering, and delivers “
complex scenes at higher bitrates than the average available data rate, improving perceived
quality.” After a quick primer on how to implement MediaMelon QBR, we’ll discuss whether
our testing confirmed these claims.
How It Works
QBR works in both VOD and live applications.
There are multiple integration modes, but the
one we tested was probably most typical, and
it involves both server and player integration
(Figure 1). Specifically, you add the QBR plug-in
at the server to analyze each encoded file and
to create a metadata map of the visual com-
plexity of the stream. You integrate QBR func-
tionality into your player via an SDK. During
playback, the player downloads the metadata
file first, which it integrates into the playback
decision tree. That is, at any specific bandwidth
level, it tells the player which stream to retrieve
based on relative quality. Communicating with
the player, the QBR dashboard tracks efficiency
savings and performance.
Figure 2 shows the playback side; note the
analysis of scene complexity on the lower left.
On the top right, the typical ABR player will retrieve streams based on bandwidth. In all three
scenarios shown, the bandwidth is sufficient to
retrieve the Medium layer.
QBR has two modes—bitrate and quality—
which you control when you integrate the SDK
into the player, though it can change from video to video. In bitrate mode, or QBR (a) in
Figure 2 (the middle option on the right),
QBR delivers acceptable quality with
maximum bitrate savings. In the figure,
you see QBR (a) dropping the data rate
during low-complexity scenes, but not
boosting it when scenes get more complex. In bitrate mode, QBR retrieves less
data than the legacy player, saving bandwidth costs.
In Quality mode, QBR delivers the best
possible quality while saving bandwidth
when it gets the chance. On the bottom
right, you see QBR (b) both decreasing
the data rate during low-complexity regions and increasing the data rate during
higher complexity regions. In essence,
the player “saves up” bandwidth for the
high-bitrate stream in the complex regions by retrieving low-bitrate streams
when scene complexity is low, improving
quality while also reducing bandwidth
costs, at least for the example shown.
MediaMelon QBR By Jan Ozer
The player side