Bossobass Dave Posted March 3, 2015 Report Share Posted March 3, 2015 Max could do a -3dBFS version on the disc (and -5dBFS, etc., until there may be a level that the Oppo can sum and pass to the SW out jack), but it seems clear to me that the Oppo is at fault. As is, the content on Max's disc is not clipped. When the Oppo is asked to reproduce that content with sats set to small and sum the low end with LFE the result is a badly clipped waveform. End of story. Link to comment Share on other sites More sharing options...
Ricci Posted March 3, 2015 Report Share Posted March 3, 2015 Either way, for me it's a simple scenario of reproducing the waveform that is on the disc out of the analog out with as little distortion as possible. I showed that even a cheap Sony AVR can accurately preserve the sine wave on max's disc with 5 channels of re-directed bass as long as the analog levels are kept in check. This is all that I'm asking for. If it is too hot of a mix and it is going to clip on reproduction, I at least want an accurate reproduction of what's on the disc without adding clipping to the clipping. Especially when sending that signal to high powered amplifiers and long throw drivers. ^This If I have to keep the SW channel gain and master set to -12 to avoid additional clipping of the signal in the line out for the worst case signal and compensate further down the chain at the amps that is fine. At least it is workable if not ideal. So far there seem to be a number of pieces of equipment, including the Oppo, where there is additional clipping and waveform distortion introduced that is unrelated to the voltage limitations of the analog output stage. There is nothing you can do to clean this up with gain structure in those cases. Dave has a good idea that it would be nice to have the WCS 7.1 track and perhaps others that are encoded at -0.5, -1,-1.5,-2,-2.5 and -3 or something like that. Perhaps some units will clean up significantly with a level just a bit down from worst case. If that is the case it is a rare signal that would actually approach full on worst case in a movie track and a unit that perhaps cleans up with a little less level might be still "good" enough. Link to comment Share on other sites More sharing options...
mojave Posted March 3, 2015 Report Share Posted March 3, 2015 As far as the 0dBTP stuff, I don't understand if this has to do with peaks that are not being detected during production (using standard level meters) and are therefore being badly distorted due to the lack of headroom on the disc or if it is a thing that happens with the signal reconstruction algorithms after the fact. All broadcasters are required to use true peak meters to conform to the latest loudness standards. Since many mixers do both broadcast and movies, I would think they would be using the meters. Probably carelessness.. Here is a free True Peak meter you can load into your DAW if you want to check anything out: X-ISM Plugin. There are also fancier versions from other vendors for purchase. Link to comment Share on other sites More sharing options...
Shredhead Posted March 4, 2015 Author Report Share Posted March 4, 2015 This is OPPO's response: The Bass Management (or LFE Re-direction) algorithm used in BDP-10X can be simplified as below: As you are applying low frequency only signals (<60Hz) to all channels and the default crossover frequency is 80Hz for the Lowpass filter, we can say that all those re-directed LFE components will be added to the LFE channel information and passed to the Sub output, so now the “new” Sub signal level can be calculated as: (for simplicity, we would treat 0.1dB as 0dB, so the original signal level in each channel is 0dB or Vmax) Sub_new = V_LFE*(-8dB) + 7*V_others*(-18dB) = Vmax * 10^(-0.4) + 7*Vmax*10^(-0.9) = Vmax * 0.3981 + 7 * Vmax * 0.12589 = Vmax * 1.28, so “new” SW signal level is beyond the maximum allowed value. This is why clipping could be added as a by product of the bass management. Based on these calculations, there is nothing wrong with the OPPO's Bass Management algorithm for the following two reasons: The signals used in this particular 7.1 channel configuration is very uncommon: no commercial disc will apply Low-frequency only signal to other channels except the LFE channel, and if those channels contains signal on the normal 20-20kHz band, a major portion of the re-directed signal will be filtered out by the Lowpass filter, thus the final Sub level won’t be high enough for clipping. The original LFE signal is set to 0dB (or 0.1dB) which is equally uncommon as commercial discs will set the LEF signal level to be 10dB lower than other channels (to leave margin for the bass management). If 10dB attenuation is for the LFE channel information, then there will be no chance of introducing clipping as part of the bass management process. In addition, in your link you have provided us, you note that the “Trim Level” doesn't help with this “LFE clipping”. The reason for this is that the Trim Level is adjusted after the bass management, so the clipping was already a part of the signal path. Reducing the trims will have no affect in this case. Regards, Lanping Link to comment Share on other sites More sharing options...
Shredhead Posted March 4, 2015 Author Report Share Posted March 4, 2015 We hooked up the old player that the OPPO replaced to compare waveforms of the HTTYD crash scene. It is a Panasonic DMP-BD85 with 7.1 analog outputs. This Panasonic has no master volume so we adjusted the fixed sub output to -12dB to avoid analog clipping. Here is a comparison of the clipped OPPO's out and the non-clipped Panasonic's out for the HTTYD Dragon Crash scene: It is obvious that the OPPO is reaching a headroom limit and clipping the waveform's peaks in real world content. Once again, the OPPO clips the real world content regardless of master volume or trim volume. This clipping has nothing to do with the voltage out of the subwoofer jack. Oh and by the way, with the trim set to -12dB, the Panny also passed the worst case 7 channel re-directed bass test: This is the OPPO vs Panny with the Panasonic preserving the peaks of the waveform. This was a player that was priced under 200 dollars when it was new and it is outperforming the OPPO with the WCS and real world source material. We ran through 9, WOTW, and OZ and for all of them there are similar parts showing clipped waveform on the OPPO for the content that is heavy on the re-directed bass. Link to comment Share on other sites More sharing options...
Bossobass Dave Posted March 4, 2015 Report Share Posted March 4, 2015 Earlier in the debate I made a similar comment to the one the Oppo tech sent Paul, namely that the content in the sats channels is not likely to be all low end at -0.1dBFS, so -0.1dBFS is not representative of actual content. But, the proof is in the pudding. The Panny passed the WCS Max Disc 40 Hz sine test with flying colors, faithfully reproducing the waveform. The SW trim was set to -12dB but the player passed a clean analog signal that my A-14K can easily amplify to my desired playback level. The Oppo flagship cannot. As far as WCS soundtracks like HTTYD, WOTW, 9, WOTT, B:LA, etc., that are in my library, many have said in the past that this is only [insert some stupid invented percentage number] of available discs. To that I reply in my neighbor's library of Tivo'd soap opera episodes, yeah, but in my collection, it's a big chunk of the total number of titles. Thanks to Shred. It was a lot of work to document what he called from the git. I said earlier that Max's disc was the last unknown but now I'm convinced that it's just a poor design on Oppo's part. Link to comment Share on other sites More sharing options...
maxmercy Posted March 4, 2015 Report Share Posted March 4, 2015 Wow....I mean, WOW. So Oppo, in catering to the 'super-high end', basically states that engineering the component to the spec is NOT part of their philosophy, nor will it be. In fact, they basically said they would rather cater to the films that are not sonically demanding. I cannot say that I will be purchasing an Oppo anytime soon...not until they realize their player cannot handle the content that we have shown is there. Too bad. Thanks for taking the time, Shred. JSS Link to comment Share on other sites More sharing options...
3ll3d00d Posted March 4, 2015 Report Share Posted March 4, 2015 I'm quite impressed they replied so openly and in such detail so quickly. It's also notable they seem to be allowing sufficient headroom for the intersample peak issue. To then fail to add the ~5dB required to cater for the absolute worst case on the bass management front seems shortsighted, for a high end product, to say the least. Link to comment Share on other sites More sharing options...
MemX Posted March 4, 2015 Report Share Posted March 4, 2015 Well, that's just saved me a grand.... lol Link to comment Share on other sites More sharing options...
Ricci Posted March 4, 2015 Report Share Posted March 4, 2015 That seals it. I'm glad they responded with actual data and promptly at that, but the measurements above show that while signals that overload the Oppo might be rare, they do occur in actual content. And as Dave pointed out these tracks might be rare in some peoples collections but in mine they are a significant percentage of the titles. I bet the EOT intro would be fairly nasty looking through the Oppo. No matter what they say about rare content and all that. The fact remains a dusty old $200 Panasonic player can preserve the waveform of the dragon crash in HTTYD with the typical bass management settings most use and the Oppo cannot. Who would've thought. Thanks for the leg work Shred. Link to comment Share on other sites More sharing options...
Bossobass Dave Posted March 4, 2015 Report Share Posted March 4, 2015 EOT intro was one of the scenes we tested. What matters with the Oppo is whether or not, in what channel(s) and how much bass is redirected to the summing block. Oppo handles WCS in the LFE channel but as soon as you add 1 channel of redirected bass, the waveform clips. Since there is no trivial way to track down the low end content, channel by channel, we just summarize that tough scenes that include redirected bass will be clipped through the Oppo. I would love to see the results of the 103 vs the 105 which we tested because the 103 has the Cirrus Logic chipset vs the ESS chipset used in the 105. Link to comment Share on other sites More sharing options...
Madaeel Posted March 4, 2015 Report Share Posted March 4, 2015 Well, that's just saved me a grand.... lol +1. I guess when the time comes it'll be the Denon for me. Thanks Paul. Link to comment Share on other sites More sharing options...
Bossobass Dave Posted March 4, 2015 Report Share Posted March 4, 2015 This exercise has been an eye opener for me. I can only now imagine what sorts of signals are being sent to subwoofers when owners routinely run +6dB, +10dB, +15dB hot by adjusting the AVR (or pre/pro or player as the case may be) trim and/or MVL. Anyone wanna buy an Oppo 105? Link to comment Share on other sites More sharing options...
Madaeel Posted March 4, 2015 Report Share Posted March 4, 2015 This exercise has been an eye opener for me. I can only now imagine what sorts of signals are being sent to subwoofers when owners routinely run +6dB, +10dB, +15dB hot by adjusting the AVR (or pre/pro or player as the case may be) trim and/or MVL. Anyone wanna buy an Oppo 105? Are you just gonna use the Panny for now? Link to comment Share on other sites More sharing options...
vxds11 Posted March 4, 2015 Report Share Posted March 4, 2015 Looks like I came back just in time. You guys are awesome. Link to comment Share on other sites More sharing options...
nube Posted March 4, 2015 Report Share Posted March 4, 2015 I guess the next question is, what pre/pro CAN cleanly accommodate the worst case scenario, or even the existing content we chronicle on this forum, at reference? The Denon looks like the only one thusfar. Doesn't this imply that a majority of the people playing at reference levels and above have likely been experiencing clipped low frequency content and thinking it was situation:normal? It makes me wonder what unclipped sounds like! Link to comment Share on other sites More sharing options...
Spacebug Posted March 5, 2015 Report Share Posted March 5, 2015 As I said before, if it is only a matter of digital headroom a nanoavr or equivalent at the input of your avr of choice should do it if you apply appropriate atennuations to the channels. Someone with a nanoavr and oscope might wanna test this theory? One might think one should not need to do this just to get clean signals out of the avr but what can you do? Seems the 5db headroom guideline by Dolby (?) is not sufficient to pass some movies. Would this be a fault of the avr manufacturer or the guidelines they seem to follow? This of course forces the source to decode to pcm first, thus breaking bitstream for anyone wanting the atmos track to atmos compatible avr for example... Link to comment Share on other sites More sharing options...
maxmercy Posted March 5, 2015 Report Share Posted March 5, 2015 I guess the next question is, what pre/pro CAN cleanly accommodate the worst case scenario, or even the existing content we chronicle on this forum, at reference? The Denon looks like the only one thusfar. Doesn't this imply that a majority of the people playing at reference levels and above have likely been experiencing clipped low frequency content and thinking it was situation:normal? It makes me wonder what unclipped sounds like! No AVR/pre-pro can do it at 0dBMV and 0dB trims (so far). The Denon requires turning down the digital in by 11dB or the SW out by 11dB for a clean WCS. A nanoAVR can also do the job. JSS Link to comment Share on other sites More sharing options...
MemX Posted March 5, 2015 Report Share Posted March 5, 2015 Thanks for the hard work in finding all this out, chaps, it's much appreciated! Link to comment Share on other sites More sharing options...
MemX Posted March 5, 2015 Report Share Posted March 5, 2015 That seals it. I'm glad they responded with actual data and promptly at that, but the measurements above show that while signals that overload the Oppo might be rare, they do occur in actual content. And as Dave pointed out these tracks might be rare in some peoples collections but in mine they are a significant percentage of the titles. I bet the EOT intro would be fairly nasty looking through the Oppo. No matter what they say about rare content and all that. The fact remains a dusty old $200 Panasonic player can preserve the waveform of the dragon crash in HTTYD with the typical bass management settings most use and the Oppo cannot. Who would've thought. Thanks for the leg work Shred. I might keep my eye out for one of these Panny's secondhand - I presume that others are similarly able to deal with WCS signals but we haven't got all the time and money in the world to test everything ever made! This exercise has been an eye opener for me. I can only now imagine what sorts of signals are being sent to subwoofers when owners routinely run +6dB, +10dB, +15dB hot by adjusting the AVR (or pre/pro or player as the case may be) trim and/or MVL. Anyone wanna buy an Oppo 105? Bosso - given we now have evidence of the 105 clipping on such scenes as you mention testing earlier, will you need to go back and look at your signal chain to ensure that a player that can handle a WCS accurately won't over-extend the drivers in your various subs? Link to comment Share on other sites More sharing options...
MKtheater Posted March 5, 2015 Report Share Posted March 5, 2015 I thought the spec lab graphs showed an almost identical representation of the source? Where would the clipping show? Link to comment Share on other sites More sharing options...
Shredhead Posted March 5, 2015 Author Report Share Posted March 5, 2015 I thought the spec lab graphs showed an almost identical representation of the source? Where would the clipping show? It did but the source was always the OPPO. We didn't catch on to the clipping until max's disc revealed it and then we A/B'd source material with a player that did not clip and the OPPO: http://data-bass.ipbhost.com/index.php?/topic/379-maxmercys-wcs-test-disc-beta-and-an-o-scope/?p=6375 Link to comment Share on other sites More sharing options...
Shredhead Posted March 5, 2015 Author Report Share Posted March 5, 2015 Bosso - given we now have evidence of the 105 clipping on such scenes as you mention testing earlier, will you need to go back and look at your signal chain to ensure that a player that can handle a WCS accurately won't over-extend the drivers in your various subs? With it's peak detector light, the SEQSS makes it stupid easy to set the gain stage of what you're sending downstream. Also, I think it is more dangerous to send an amplified clipped signal to drivers than a dynamic source. I know there are a lot of people on the internets that disagree but they probably use consumer sub stuff with limiters and filters. Link to comment Share on other sites More sharing options...
Shredhead Posted March 5, 2015 Author Report Share Posted March 5, 2015 As I said before, if it is only a matter of digital headroom a nanoavr or equivalent at the input of your avr of choice should do it if you apply appropriate atennuations to the channels. Someone with a nanoavr and oscope might wanna test this theory? One might think one should not need to do this just to get clean signals out of the avr but what can you do? Seems the 5db headroom guideline by Dolby (?) is not sufficient to pass some movies. Would this be a fault of the avr manufacturer or the guidelines they seem to follow? Good questions. Other than raising the noise floor and therefore decreasing dynamic range, I don't know that there would be anything else bad about attenuating with the nanoavr. The only other thing might be an increase in jitter error due to the clock of the nano. Maybe worth looking into if it was ever tested with something like the audio precision. OPPO has been dancing all over the issue with our recent email discussion. First they sent me this: On 3/3/2015 at 1:00 PM, "OPPO Service" <service@oppodigital.com> wrote: The Bass Management (or LFE Re-direction) algorithm used in BDP-10X can be simplified as below: -This shows a 15dB attenuation of all re-directed channels after they get lowpassed. Then when I pressed them for an answer on why they're bass management clips incoming signals but a 200 dollar player and cheapo AVR's do not clip when summing bass they responded with: "Other brands, especially receivers and pre-processors, may perform their Base Management, Channel Trims, and master volume in a different sequence or even using different processing parameters. For example, one of our Denon receivers will attenuate all input signals by 15dB before doing any processing, and later boost the signal level back after the digital-to-analog conversion (DAC). Your Panasonic BD85 may put the sequence in a similar way the Denon does." Are they conforming to spec or not?!?! Well, evidently not if it clips is my guess. I keep asking if they will put out a firmware update to properly attenuate the levels of the re-directed bass channels to avoid clipping and I get things like this: "Unfortunately based on what you are requesting and the likely lowered audio performance if we change it so that the channel trims occur before the DAC, it is just not likely that we will make a firmware available to correct clipping due to the source being hotter than the Dolby and DTS specifications are designed for." -Blaming it on the source. Yeah OPPO, it will lower the audio performance a ton if you guys STOP YOUR PRODUCT FROM FROM CLIPPING!?!?!? For anyone curious, the customer service experience that OPPO provides might as well be a pre-recorded message that hangs up on you. Link to comment Share on other sites More sharing options...
Bossobass Dave Posted March 5, 2015 Report Share Posted March 5, 2015 I think you should start a thread at AVS in the players forum see how Oppo responds to that. Link to comment Share on other sites More sharing options...
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