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Topic: How can you compare different encoders from a technical standpoint? (Read 879 times) previous topic - next topic
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How can you compare different encoders from a technical standpoint?

Basically, I am testing out different AC3 5.1 encoders, and other than spectral analysis and listening tests is there any additional ways to compare which of them produces a "superior" encode? I can't hear a difference between them since I am not exactly trained for this kind of thing and in terms of spectograms two of them seem to look practically identical. It would be nice to know which encode is closest to the lossless source.

I can provide more information and the spectrals if someone knows what to look for.

Re: How can you compare different encoders from a technical standpoint?

Reply #1
Spectrogram is a misleading tool: it won't help you to know which perceptual encoder is better. Your spectrograph is more or less useful to see what is missing (lowpass). But all these encoders are transforming the signal, and you won't see how the remaining frequencies have changed. Some modern encoders are able to reach or go beyond 20 KHz at 48 kbps but they obviously sound worse than most other encoders at 192 kbps and lowpassed to 16…18 KHz. A quick look to the spectrograph simply tells that 20 Khz is better than 16 KHz and not how different or dirty the 0…20000 Hz are.

There are no other ways than ABX to check how good an AC3 encoder is. If you cannot hear any difference then you have your answer: your AC3 encoders are all perceptually identical. Now you can try to lower the bitrate and check when start the bitrate starvation and related audible issues.

Re: How can you compare different encoders from a technical standpoint?

Reply #2
Spectrogram is a misleading tool: it won't help you to know which perceptual encoder is better. Your spectrograph is more or less useful to see what is missing (lowpass). But all these encoders are transforming the signal, and you won't see how the remaining frequencies have changed. Some modern encoders are able to reach or go beyond 20 KHz at 48 kbps but they obviously sound worse than most other encoders at 192 kbps and lowpassed to 16…18 KHz. A quick look to the spectrograph simply tells that 20 Khz is better than 16 KHz and not how different or dirty the 0…20000 Hz are.

There are no other ways than ABX to check how good an AC3 encoder is. If you cannot hear any difference then you have your answer: your AC3 encoders are all perceptually identical. Now you can try to lower the bitrate and check when start the bitrate starvation and related audible issues.

I'll definitely try encoding at lower bitrates, that seems like an obvious way to see which starts failing first.  Thanks for the suggestion and help.

 
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