Ik zag tijdens het installeren van v9.9.5 dat het nieuwe audioformaat .Opus
ook ondersteunt wordt
Opus has been shown to have excellent
quality, and at higher bit rates, it turns out to be competitive with codecs with much higher delay, such as HE-AAC and Vorbis.
In listening tests the codec shows superior quality compared to HE-AAC codecs, which have so far been dominant in that area because of their use of the proprietary spectral band replication (SBR) technology.
Opus has very low algorithmic delay, a necessity for use as part of a low audio latency communication link, which can permit natural conversation, networked music performances, or lip sync at live events. Total algorithmic delay for a codec is the sum of delays that must be incurred in the encoder and the decoder of a live audio stream regardless of processing speed and transmission speed, such as buffering audio samples into blocks or frames, allowing for window overlap and possibly allowing for noise-shaping look-ahead in a decoder and any other forms of look-ahead, or for an MP3 encoder, the use of bit reservoir.
Total one-way latency below 150 ms is the preferred target of most VoIP systems, to enable natural conversation with turn-taking little affected by delay. Musicians typically feel in-time with up to around 30 ms audio latency, roughly in accord with the fusion time of the Haas effect, though matching playback delay of each user's own instrument to the round-trip latency can also help. It is suggested for lip sync that around 45-100 ms audio latency may be acceptable.
Opus permits trading-off quality or bitrate to achieve an even smaller algorithmic delay (5.0 ms minimum). While the default Opus frame is 20 ms long, a further 2.5 ms lookahead is required for window overlap in the CELT layer and noise shaping in the SILK layer, typically giving a delay of 22.5 ms. The SILK layer's minimum is 10 ms frames (12.5 ms delay), while the CELT layer's minimum is 2.5 ms (5.0 ms delay).
Nu ben ik erg benieuwd hoe .Opus, vergeleken met MP3 en Vorbis, in mijn eigen
Ook Winamp ondersteunt
.Opus (middels een third-party .DLL), evenals (de nog uit te brengen nieuwe versie van) de audio-encoder Fre:Ac
Het wordt nog spannend: toekomstige ondersteuning voor het H.265
videoformaat en .Opus in menig video-encoder, maakt .AVI/.MKV bestanden van een zéér hoge kwaliteit mogelijk
[Reactie gewijzigd door John Stopman op 2 juni 2013 14:29]