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Property:Codec
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Term
| Term: | Codec | Wiki | Freetz | IPPF | whmf | AVM | Web |
| Short for: | Coder / Decoder | ||||||
| Location: | Lexicon >> File-Formats | ||||||
| Weblinks: | Wikipedia.int - Wikipedia.de | ||||||
| Description: | Encodes / decodes media to / from a specific File-Format | ||||||
Goto: FRITZ!OS - SMW-Browser
Details
A Codec is a device or software which encodes or decodes media to or from a specific File-Format.
Codecs are mainly used for storing or streaming audio or video data, often using compression.
Compression is either lossless, so the original data is preserved after decoding, or lossy where it's not.
Lossy compression reduces data by approximating the original, fooling our senses, but the original data is lost.
FRITZ!OS
Speech-Codecs
Telephony targets at the frequency spectrum required for transmission of human speech, which is a subset of what's required
to reproduce music. That's why Telephony uses an own set of Codecs.
See the VoIP, RTP, DECT, ISDN and TAM articles for the Codecs used.
This will be moved to the G.729 article:
Some Codecs are non free, like G.729, which has been patented until 2017-01-01. Although the patent expired there are still
copyright issues if the Codec is implemented based on the example code. See this asterisk G.729 thread and the solution.
That's why licenses are still sold today, on a per stream base.
FRITZ!OS implemented G.729 since 2005, but it was not enabled by default. To enable it (and possibly a second non free
Codec) AVM uses 2 hidden TFFS variables codec1 and codec2, which have to contain a license key. These keys are accessed
by libtffs.so for voipd, telefon, dect_manager and codeclicence.
To preserve these keys a Recovery.exe retrieves them since fw 3.56 before creating a new TFFS, see get-codecs.
See also the AVM knowledge base document about Supported VoIP Codecs, which does not name G.729.
Audio-Codecs
Generic audio Codecs target at reproducing the frequency spectrum an average human ear could perceive.
They are used for encoding music or for the audio part of videos.
In FRITZ!OS generic audio Codecs are used by ffmpegconv, playerd and streamer.plugin , for Transcoding to speech Codecs,
