The table below shows codecs features:
|AMR GSM 06.90||20 ms||8 KHz, 16 bit, Mono||Bitrates: 4750, 5150, 5900, 6700, 7400, 7950, 10200, 12200; a discontinuous transmission mode (DTX) available with 1750 bps non-speech frames|
|G.726||8 ms||8 KHz, 16 bit, Mono (a-law, μ-law native support possible)||Bitrates: 16000, 24000, 32000, 40000|
By the way, packaging more speech codecs into DMO interface is expected to come soon. With a certain luck it would go even farther to video coding…
I would also need to make a summary table on input/output formats, bitrates etc.
Chances are that the following are also to be put into DMO:
The mix of the technologies works very well.
All together – AMR GSM 06.90 Speech Codec DirectX Media Object (DMO) as shown below:
Runtime requirements include:
So, DirectX Media Objects (DMO) appeared to be a nice interface to extend DirectShow functionality. I could quite easily create encoder/decoder pair of DMOs for AMR speech coding (GSM 06.90). Reasonable ease and development speed. I will probably even prepare an informational version and put here on website. It is likely to contain forced silence intevals because it’s a licensed stuff and can’t be distributed freely.
How could it happen that an expreienced DirectShow guy only recently discovered DirectX Media Objects (DMO)? And the idea is really nice. Definitely got to check this at work with some audio processing.
= Serious Problems
A customer, a very loyal one, I must admit, installed several multichannel digital video recorders. He reported a few problems and more or less quickly we fixed all nut one. Serious system fails about one per 1-2 days and noone can tell the reason. Logs don’t show problems, it may be fauly hardware too (enough cases known in past), any ways to come out of this are appreciated. I wish we could fix it, the customer is very good.