Pioneer SC-LX904 AVR Delayed Audio Start over HDMI? It makes me twitchy!

[JCAV]

I've been going a bit batty trying to troubleshoot an issue with this receiver exhibiting an annoying delay of a few seconds in locking and promptly starting Dolby Digital or DTS audio bitstreams over HDMI.

Admittedly, this is a minor issue. But on a beautiful $3K flagship AVR, I find that it now just grates on me.

When starting a Blu Ray disc or DVD with Dolby or DTS audio soundtrack (either from my Pioneer BDP-85FD player or my Sony PS3), the receiver takes anywhere from 3-5 seconds to begin playback of the audio. The video signal is processed immediately, but the audio start is delayed. This is not a sync issue. Once the audio bitstream is started, it remains in sync with the video signal. The audio just doesn't start immediately upon playback as it should.

I can see the HDMI indicator flashing on the front panel during these few seconds at playback startup. The receiver appears to be taking some extra time trying to identify the audio format and then begins decoding and playing the audio signal.

I never had this issue on my previous generation receiver (Pioneer SC-27), which I still have running on my basement system. When I connect my BDP-85FD to my SC-27, DD and DTS signals begin instantaneously at the start of playback. This, along with the fact that I see the problem from the PS3 as well, clearly points to a problem with the LX904.

The other interesting aspect is that the LX904 does not have this problem with all digital audio formats. It has no problem instantly decoding audio signals from PCM and DSD (SACD) bitstreams. Only on Dolby or DTS soundtracks. What makes this doubly irritating is that it affects many Blu Ray Pure Audio discs which contain high resolution audio in DTS HD MA format in addition to virtually all video titles.

Converting DD and DTS to PCM is one workaround, but one that doesn't sit well, especially as it foregoes the benefits of Atmos processing on newer titles.

I contacted Pioneer Technical Support and we went through all myriad of different settings between the receiver and the Blu Ray player to see if a particular configuration was the culprit. No combination of settings we found could resolve the issue. I have installed the very latest firmware on the LX904 that was just released back on May 18 to no avail.

The technician concluded that my receiver must have a defect and advised that I send it in for service.

Before going to the trouble and expense of sending the unit in for service, I thought it would be interesting, just for kicks, to take my older generation Blu Ray player in the basement (it's a Pioneer BDP-23FD) and connect it to my LX904 in the living room to see if made any difference. I fully expected to encounter the same problem. But to my surprise, the DTS HD Master Audio and Dolby True HD bitstreams sent from the 23FD started playback instantly on the LX904.

At that point, I did triple check my different HDMI cables between the players and the receiver to make sure I didn't have a problem with a cable. Changing cables made no difference. The LX904 consistently delayed playback from the 85FD but started playback immediately from the 23FD.

What now seems most likely is that the issue has something to do with the HDMI implementation between different combinations of devices.

In searching the net for more information, I read with interest that @Todd Anderson in his recent post on this site made mention of an HDMI 2.1 bug found in some receivers that implemented Panasonic's chipset.

I'm wondering if anyone knows if there is a known HDMI chipset bug that also causes this audio handshake/delay issue?

In reading more on this known Panasonic chipset issue, the bug causes serious problems with high resolution/high frame rate video processing. This raised another concern for me about my LX904.

I have no idea if I'm affected by this video issue because for now I'm still clinging to my beloved Kuro Plasma 1080p display. I am contemplating the leap to 4K soon (a Pioneer 4K TV sighting at a Best Buy over the holidays resurrected a glimmer of hope that Pioneer might jump back in the high end display market with an amazing new Elite model, but from what I've read, the new Pioneer 4K TV is a branded TLC targeted at the general consumer market rather than the high end).

And, yes, I fully admit, I am a Pioneer Elite fanboy going back to my first AV NIRVANA experience in the late 90s when I saw a demo of a Pioneer Elite Laserdisc player and Receiver. All frustrations with VHS and dreadful old school cable TV vanished in one glorious moment! So, it is with relief and excitement that I read in this forum that Pioneer Elite has survived its near death experience and will hopefully comeback stronger!

Sorry, digressing!

Anyway, does anyone happen to know what HDMI chipset is implemented in the Pioneer SC-LX904? Is it one of the dreaded Panasonic ones?

My prayer would be that this audio issue could be something that could be fixed in firmware or by some combination of settings that I've overlooked. But I am assuming that if it is a chipset problem, there's no hope except to upgrade to a newer unit with a non-flawed chip. This thought makes me sad because the LX904 is in most all other respects a marvelous machine.

Anyone that might have more info or tips/tricks to share around understanding the root cause of this HDMI audio delay issue or a resolution is most greatly appreciated!

 

[Todd Anderson]

Hey there - sorry you're experiencing this. It's funny how these small annoyances can become particularly upsetting once you begin dissecting them.

First off, the Panasonic chipsets that were flawed were HDMI 2.1, implemented by Yamaha and Denon/Marantz. If memory serves, the LX-904 is a 2019 release with HDMI 2.0a functionality (correct?). I wouldn't be concerned about faulty chipsets.

What you're describing is a fairly common occurrence. I'd be willing to bet that if you switch your Blu-ray player's output to PCM (if the player is capable of decoding audio codecs), your issue would disappear. I think it just boils down to a 2-3 second delay where the 904 begins decoding the incoming bitstream audio info. I have a very similar, albeit shorter, audio delay with my StormAudio processor. An image shows for about 1.5 seconds before the sound joins.

My only suggestion would be to make sure the firmware on your Blu-ray player is up to date. Aside from that, you're probably operating in the range of normal.

 

[JCAV]

Thanks so much for the response, Todd!

I confirmed I have the latest firmware on the two Pioneer Blu Ray players I'm experiencing different results with (the BDP-85FD and the older BDP-23FD), as well as the latest firmware on the 904.

The mystifying thing is why the 904 begins decoding the audio bitstream instantaneously from my much older BDP23-FD Blu Ray player, but it takes several seconds to begin decoding the audio bitstream (on the exact same disc) from my newer generation BDP85-FD model.

Seems logical that the decoding function on the 904 would cause a delay consistently regardless of the HDMI source. I'm intrigued as to what could account for the difference? Maybe something do with the handshake and buffering process within the HDMI signal? Could the earlier generation BDP23-FD be using an earlier version of the HDMI specification which doesn't run into the handshake delay on the 904's processor?

Normal as it may be, I still wonder if it could be something that could be corrected or improved in the 904's firmware. I'd interested to know what a low level engineer at Pioneer would have to say about it. But, thankfully, it's more of a curiosity and an annoyance than a major issue.

Thanks for the great content on this site and for the regular Pioneer/Onyko updates!

Cheers!