[opus] Info OPUS encoder

Edwin van den Oetelaar oetelaar.automatisering at gmail.com
Wed May 15 02:26:47 PDT 2013

Hallo Christiaan,
groeten uit Nederland.

Opus info :

Frame sizes from 2.5 ms to 60 ms

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

Opus permits trading-off quality or bitrate to achieve an even smaller
algorithmic delay (5.0 ms minimum).[26] 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).[27]

This is from the wiki page.

If you want to out-source some of your work integrating the codec into
your product, give me a call. (I am within 30 minutes from your

Edwin van den Oetelaar

On Wed, May 15, 2013 at 9:47 AM, van Bijleveld Christian
(ST-CO/ENG1.3) <Christian.vanBijleveld at nl.bosch.com> wrote:
> Hello,
> I am testing the command line based opus encoder/decoder tools and I have
> some questions regarding the information given by the encoder (see below as
> an example).
> Encoding using libopus 1.0.2 (audio)
> -----------------------------------------------------
>    Input: 48kHz 1 channel
>   Output: 1 channel (1 uncoupled)
>           20ms packets, 64kbit/sec VBR
> Preskip: 312
> Encoding complete
> -----------------------------------------------------
>     Encoded: 6.86 seconds
>     Runtime: 1e-06 seconds
>              (6.86e+06x realtime)
>       Wrote: 57354 bytes, 343 packets, 9 pages
>     Bitrate: 66.0921kbit/s (without overhead)
> Rate range: 48.8kbit/s to 110.4kbit/s
>              (122 to 276 bytes per packet)
>    Overhead: 1.19% (container+metadata)
> More specifically, I am interesting in knowing how should I interpret the
> Runtime information ‘6.86e+06x realtime’, the Bitrate detail ‘without
> overhead’ and the Overhead figure 1.19%.
> I have also a question regarding the delay introduced by OPUS: is the delay
> from encoder to decoder equal to the audio packet size (in this case, 20ms)?
> And, what is the minimum encoder-decoder delay that can be achieved with
> Thanks in advance.
> Met vriendelijke groeten | Best Regards,
> Christian van Bijleveld
> _______________________________________________
> opus mailing list
> opus at xiph.org
> http://lists.xiph.org/mailman/listinfo/opus

More information about the opus mailing list