The hidden dangers of audio transcoding

Posted on July 19, 2013 by

Transcoding is a danger to call quality and even call viability.

The issue is, translating codecs can cause data loss and transmission interruption. Audio packets aren’t physically passed from one network to another. The transmitting network shows the packet to the receiving network, and the receiving network makes a copy of what it sees. In a sense, the receiving network paints a picture using images it can work with, adding a note for the next leg to transcode the data back into the original format.

Think about it as three translators sitting between you and someone you’re speaking with. When you say something, one translator translates it into a language the middle translator understands. The middle translator then carries the message to the translator working for the person you’re speaking with. The last translator then translates the message back to the language you started with for the person you’re trying to talk to. Sound convoluted? It is.

In Google Translator, it looks like this:


“It’s like you’re having a conversation with someone and there’re two translators between you.”

Translated into Japanese and back (Google):

“There is a translator between the two of you and what you would like to have a conversation with someone.”

Now, imagine each word above is a data packet in your VoIP transmission. How’s that crucial business introduction call sounding? Garbled, jittery, even dropped conversations aren’t only annoying, frustrating, and damaging to your business flow, they leave a bad taste on your brand image. As humans, we like to be able to hear clearly. Clients and customers who repeatedly struggle through inaudible conversations when calling into your business, might up saying yes to someone else they can actually talk to.

Quality is a main reason to stay away from HD audio codecs for call that aren’t staying native to your own internal network. Because as soon as a call leaves your network, it’s hard to know exactly where it’s going to go. And chances are, it’ll find its way onto the PSTN.

The telephone game is one played with fractions of a penny. Sometimes, even “on-net” (within the same carrier) calls are sent off-net and brought back to save a few hundredths of a penny. So for the sake of a sliver of profit, your external calls are probably going to hit the PSTN.

Of course, even more obvious than that is, although it’s 2013, not everyone is using a VoIP connection. And in order to connect a VoIP call to a PSTN destination, there will be transcoding.

So, for the foreseeable future, using audio codecs that aren’t standard on PSTN gateways is impractical. It adds complexity to your transmissions, and threatens call quality. If wideband HD voice is really something you want, use it internally where you know calls will never be transcoded, or on a line you know for certain will never touch the PSTN. But to protect your connections and your image, everything else should be routed according to the standards of the network your calls are inevitably going to be routed through.