Evalvid
overview
Contents
•
•
•
•
Introduction
Framework and Design
Functionalities
Tools
Introduction
• Publicly available tools for video quality
evaluation often assume synchronized frames
at the sender and the receiver side, which
means they can’t calculate the video quality in
the case of frame drops or frame decoding
errors
• Evalvid: evaluation of transmission-distorted
video
• Trace files
Framework and Design
Functionalities
• Determination of Packet and Frame Loss
• Determination of Delay and Jitter
• Video Quality Evaluation
Packet loss
• unique packet id -> cancel the effect of
reordering.
• which kind of data is in the packets
Frame loss
• 1 frame can be paketized in many packets ->
frame loss
Determination of Delay and Jitter
• play-out buffer
– This would eliminate any possible jitter at the cost
of a additional delay of the entire transmission
time. The other extreme would be a buffer
capable of holding exactly one frame. In this case
no jitter at all can be eliminated but no additional
delay is introduced
– Delay the Entire video -> big size possible
• The formal definition of jitter
• variance of the inter-packet or inter-frame
time.
• The “frame time” : the time at which the last
segment of a segmented frame is received.
Video Quality Evaluation
• two approaches to measure digital video
quality
• subjective quality measures
– impression of the user
• Objective quality measures
– metric
PSNR: closed to subjective evaluation
PSNR -> MOS
Tools
Files and Data Structures
• Raw (uncoded) video files
• trace files
VS - Video Sender
• generate a trace file from the encoded video
file
• two trace files containing information about
every frame in the video file and every packet
generated for transmission
ET - Evaluate Traces
• calculation of packet and frame losses and
delay/jitter takes place
• three trace files
ET (cont)
• ET can also take into account the possibility of
the existence of certain time bounds.
– Playout buffer
• generation of a corrupted (due of losses)
video file
FV – Fix Video
• Digital video quality assessment is performed
frame by frame. Therefore, the total number
of video frames at the receiver side, including
the erroneous frames, must be the same as
that of the original video at the sender side. If
the codec cannot handle missing frames, the
FV component is used to tackle this problem
by inserting the last successfully decoded
frame in the place of each lost frame as an
error concealment technique
PSNR
MOS
3rd party tools
• TCP dump: phan tich luu luong