Technologies

Perceived video quality measurement technologies

AccepTV has developped several video quality measurement technologies (commonly called "video quality metrics") :


All these metrics are the result of many years of research in the fields of human vision modeling, perceived quality evaluation and video processing.

To design a perceived video quality metric, we develop vision models in order to reproduce human perception of video. Then we apply these models to videos from which we extract features which are relevant to human judgment of video quality. At last, we combine several measures performed on these features in order to compute video quality scores. These video quality scores are compared to the ones which are given by human observers during subjective video quality assessment tests (these tests are performed in normalized viewing conditions). A metric is validated only if it provides video quality scores which are well correlated to subjective video judgment over an important number of videos.

Other quality measurement technologies

AccepTV has also developped several other metrics (audio quality metrics and specialized metrics) :
  • a jerkiness metric
  • On connected devices, if the bandwidth is too reduced with respect to the streaming bitrate, the video can suffer from jerkiness (image freezing) during playback (for rebuffering).

    And concerning jerkiness, Video Quality Monitor (VQM) has a unique metric to measure the impact of jerkiness on perceived video quality. Indeed, Video Quality Monitor (VQM) can measure perceived video quality based on encoding distortions (blockiness, blur, etc.) but also by taking jerkiness (image freezing) into account. Our jerkiness metric takes into account the number and durations of freezing events (due to rebuffering events) to compute the perceived video quality due to these problems. Subjective tests show that human observers prefer a long freezing event rather than several shorter freezing events. Our jerkiness metric reproduces that too! <>So now you can measure the impact of rebuffering events on perceived video quality for services like YouTube (for example)!

  • a no-reference audio quality metric, available in Video Quality Monitor (VQM)
  • a full-reference audio quality metric, available in Video Quality Analyzer (VQA)
  • a reduced-reference audio synchronization metric, Audio Video Sync & Quality Monitor (AVSQM)
  • a reduced-reference video synchronization metric Audio Video Sync & Quality Monitor (AVSQM)

Other technologies


AccepTV has also developped C/C++ libraries to decode video files using DirectShow filters. For example, these libraries enable to:
  • decode video and/or decode audio
  • process video with DirectShow filters (including codecs)
  • capture videos from SDI/HDSDI/HDMI or IP interfaces (UDP, RTP)
  • capture to memory or directly to disk (this may require fast hard disk drives arrays)
  • play videos on SDI/HDSDI/HDMI
  • perform simultaneous play and capture operations

AccepTV has also skills in:
  • network and web technologies: TCP, UDP, SNMP, FTP, SMTP, HTTP, PHP, javascript, etc.
  • DirectShow applications for Windows Mobile devices (capture, playing, video processing, video filtering)

At last, AccepTV has developed software to process audio and video streaming in real time under Linux.