View Full Version : Delayed auxiliary audio

12-21-2011, 08:28 AM
I recently tried hooking up the NP3900 to my old television. The old CRT television has one small speaker on the side and poor sound quality. Fortunately it has a headphone jack. I connected this to the NP3900 auxiliary input and selected "MP3 Link" in the NP3900's main menu.

It turns out that the NP3900 cannot be used for this purpose. The NP3900 delays the audio by a substantial fraction of a second. This makes programs with speaking persons unwatchable: voices do not sync with lips. Sigh.

I don't know whether this shortcoming can be overcome in software, but I'll say it anyway: it would be nice if this were fixed. I can understand how sound processing might introduce a delay; but it would be nice if there were at least negligible delay in Direct Source mode.
Thomas Hood

12-21-2011, 12:40 PM

Now you need to admit that the NP3900 is not made to amplify sound from a television....quite an odd idea in fact...I don't think this is something to fix vs. couple of other major bugs.


12-22-2011, 06:04 PM
The NP3900 has an auxiliary audio input and is thus made to amplify sound from external devices.

But due to a large delay in the sound, it can't be used to amplify sound from any external device, such as an iPod Touch or television, that also shows video. This is an unfortunate and inconvenient limitation, and one that isn't clearly communicated to the buyer.

Philips - QK
01-03-2012, 01:03 AM
Dear users,

We would like to give you more information on this:

The NP2900 / NP3900 / NP3300 / MCI8080 / MCI900 are using digital sound-processing technology. They all do transform all its input signals to the digital domain to …

a) Ensure the lowest possible noise level / get highest possible Signal to Noise Ratio (SNR)
b) Enable advanced sound-processing

The advanced sound-processing is …

1) Creating a real flat frequency response coming out of the speakers (for all Network players, NP2900,NP3300,NP3900) – direct source
2) Creating a basis for bass / treble boosting without having distortions on it outputs, no matter which loudness or setting is used
3) Creating a basis for FullSound® technology, which does regenerate signals which got lost during compressing to MP3/WMA

This advanced sound-processing system may create some delays w.r.t. time between the input and the output (e.g. speakers / headphones). This delay could cause
a noticeable issue w.r.t. lip-sync when connecting it to a TV as an amplifier. In modern TV’s you can adjust the audio delay (lip-sync synchronization) to compensate
this kind of delays. In the MCI900 and MCI8080 unit the internal DVD-player and speakers are in sync and there is no audio delay (lip-sync issue).

Hope this explains. Thanks a lot for your participation in the forum!

Kind regards,
Philips Moderation Team

01-09-2012, 11:05 AM
Thanks to Philips-QK for this informative reply.

I will reply to one point, however. Philips-QK writes:

In modern TV’s you can adjust the audio delay (lip-sync synchronization) to compensate this kind of delays.

With new TVs that I have looked at you can add delay to the audio output, not to the video output. On my Samsung TV you can delay the audio output on the S/PDIF channel only, up to 100 ms. But in order to compensate for the NP3900's (audio) delay you would have to delay the video output by the same amount.

Even if it were possible to delay the video output from the television, doing so would not be a complete solution since a TV can be used to display video and audio from a video game and in that case it isn't desirable to introduce a significant delay relative to user input.

(Besides all this, the TV I wanted to connect the NP3900 to is old and doesn't have any delay controls at all.)

Let the conclusion be that the NP3900 simply isn't suitable for use as a TV loudspeaker.

To Philips's credit, what is labeled as an "AUX input" on the back of the unit is described more narrowly in the user interface as an "MP3 Link".

01-10-2012, 02:59 PM
I'm really please I did some further research before taking the plunge and buying the N3900 as this issue is a real deal breaker for me.

I currently have an old micro HiFi in he bedroom and wanted to replace it as the 3 CD trays are on their last legs, but it's about 10 years old now. My issue is that I have a Virgin Media Cable box and a monitor without speakers. The Cable Box has the phono plugs connected into the stereo as the only audio source available.

If there are issues with audio delay then the N3900, which was top of my list of options, is sadly off the list.

This seems like a really basic issue that should be corrected.

01-10-2012, 03:03 PM
Hi sugarfix, what is your question?

01-10-2012, 03:22 PM
I didn't ask a question.

I posted to raise the point with Philips that if there is a significant audio delay on the AUX input then that has stopped me purchasing.

Also, although I didn't do so in my first post, I'd like to thank jdthood for alerting me to the issue before I spent a lot of time and money finding out for myself.

01-11-2012, 08:27 AM
Hi sugarfix,

Phillips-QK explained above that the delay is a side effect of A-to-D-to-A conversion in the NP3900. Although many digital signal processor chips are programmable, I think that it is highly unlikely that anything can be done to reduce the audio delay in the NP3900 by means of firmware changes. It's probably a shortcoming of the hardware design of the NP3900 which, as k1200rs pointed out earlier, after all isn't marketed as a TV speaker. The auxiliary input is described as an input for an MP3 player.

Googling around a bit I discovered that many people are reporting the same shortcoming in products made by other manufacturers including, for example, Sony and Onkyo.

Video and audio are never perfectly synchronized. Just moving the sofa one foot further away from the loudspeakers adds 1 ms delay to the sound reaching your ears. The problem is that in recent years both video and audio are being increasingly processed (for resolution enhancement, surround-sound effects, multi-speaker synchronization, etc.) which can result in delays in one channel relative to the other of tens or hundreds of milliseconds. Above a certain threshold, in the vicinity of 100 ms, the difference becomes noticeable.

Skew can be compensated for by delaying the "faster" channel, but as I mentioned earlier this isn't a complete solution because you don't want to delay the audiovisual output of a gaming console.

The real solution is to keep total delay well below the 100 ms threshold. Achieving this may require careful design and more expensive components. Excess delay may, for example, be the result of daisy chaining several DSP chips, each of which adds tens of milliseconds of delay. The total delay could then be reduced by doing all processing on a single chip, but this might increase the parts cost.

Clearly, as you say, audio delay is an characteristic of contemporary audio equipment that needs to be taken into account before the purchase is made.

04-16-2012, 12:23 PM
Phillips-QK explained above that the delay is a side effect of A-to-D-to-A conversion in the NP3900.

The device has a digital audio out, which makes you wonder why it doesnt have a digital audio in, saving the conversion time.

There is also a direct source option in the settings, which surely could act to turn the conversion off. Beats me why this wasnt implemented :(