Gapless CD playback. Why has this become a "feature" rather than the bleeding obvious?

[2leftears]

By the way, I looked it up… CDs spin at a constant linear velocity… approximately 200 rpm at the edge and 500 near the center. The speed it spins is dictated by the CD format itself, not the player. A DVD player plays a CD at 1x just like a CD player does. If you noticed that a DVD player was spinning faster, you were looking at it while playing a center track and comparing it to a CD player playing an edge track.

There’s no reason why playing a CD on a DVD player would be any different than playing it on a CD player.

Not true I'm afraid. I have different CD players where I can SEE the cd spin (I have serviced the things and I am well aware of how fast (or rather, slow) music CDs are spinning on 'old-school' players.)

On My Marantz the music CD (Mark Knopfler, Cal, FWIW, but any music CD with a good contrasty visible label will do) spins at the normal 500rpm when playing near the center, 200rpm near the edge. It spins slowly, and very noticeably slows down as the laser progresses towards the edge.
On My PURE CHRONOS CD player however I can SEE it spin FAR faster (at least 4x faster) on the first track, and the spin speed also doesn't drop nearly as much as on My Marantz when playing the last track; on the last track the PURE CHRONOS spins it maybe 6x faster if not more more compared to my Marantz, although at those speeds the difference between 4x faster or 6x faster is hard to estimate: it is a fast-spinning mess my eyes can't follow at all.

Playing the last track on my Marantz the CD spins so slowly that I can almost follow the label with my eyes going around as it is spinning, but playing the same last track on the PURE CHRONOS the label is still a total blurred mess so fast it is spinning.

Hence the bit on Wikipedia referring to the music CD spin speed is well out of date re. some modern mechanisms.
If you read my previous posts you realise I said that the 500rpm-200rpm spinning speed is the way transports used to read CDs (and many still do), reading the track frames continuously in one go at approx. 1.2m/s-1.4m/s linear readout speed, but there are now also plenty of transports that use different readout servo control that spins music CDs much faster than that and read the cd track intermittently, bit by bit, in segments rather than continuous. Obviously the FIFO buffer topology logic must be implemented differently in those players compared to the logic used in earlier players as they have to make sure the intermittently read frames are matched up in the buffer prior to de-interleaving, something the old-school continuous readout method doesn't need to worry about.

 

[bigshot]

Well… you can feel free to google it. Everything I found said that CDs are read at a steady, consistent speed with the rotation correcting for the real estate covered in each rotation. Constant linear velocity. They don’t read and buffer. It says DVD players play CDs the same way CD players do.

 

[sander99]

Well… you can feel free to google it. Everything I found said that CDs are read at a steady, consistent speed with the rotation correcting for the real estate covered in each rotation. Constant linear velocity. They don’t read and buffer.

It seems that your information is outdated and that things have changed. (By the way: cd players have always buffered data on some scale, be it smaller, otherwise they can not work.)

 

[2leftears]

Well… you can feel free to google it. Everything I found said that CDs are read at a steady, consistent speed with the rotation correcting for the real estate covered in each rotation. Constant linear velocity. They don’t read and buffer. It says DVD players play CDs the same way CD players do.

I googled it many times. Much of that is regurgitating the same outdated info.

I'm not BLIND. On some transports music CDs spin VISIBLY a lot (as in multiple times) faster than on traditional transports, regardless of playing the first or last track.

CD players have been buffering since the year dot as the disk rotational speed is not accurate enough, besides, the de-interleaving of the CIRC encoding absolutely requires buffering; the music samples come off the CD in the wrong order. When ASP (anti-shock protection) was introduced on the early generation portable CD players this involved a bigger buffer, and pre-loading the buffer (hence the short wait before the music started.) As time progressed this buffer got bigger, but also reading was now intermittent at a higher read-speed so that the buffer could be topped up faster when there were more read errors, and thus shock resistance was improved even further (and the pre-load time was thus also shorter).

 

[bigshot]

Maybe you can find some verification that CDs are played differently. Everything I found said that CDs and DVDs play with constant linear velocity.

 

[2leftears]

Maybe you can find some verification that CDs are played differently. Everything I found said that CDs and DVDs play with constant linear velocity.

Seeing that almost everyone on the web is regurgitating the same out-of-date 'facts' it is difficult to find technical evidence to the contrary (for obvious marketing reasons all technical specs concentrate on maximum read speeds rather than minimum read speeds when reading music CDs on USB drives, and regular CD players marketing doesn't find it worthwhile mentioning).

Asked to provide evidence for something that is quoted incorrectly everywhere based on outdated information, obviously I have a problem. But I stand by my observation. The difference between SEEING 200rpm vs 1000rpm isn't a matter of perception bias. (or hearing the vibration difference in my DVD & BluRay players on poorly balanced disks for that matter.

But maybe this is a good start (also mentions the gapless playback issue when playing music CDs):

https://community.volumio.com/t/volumio-running-cd-drive-at-noisy-high-speed/54246

Also, Pioneer has its "Persistent Quiet Mode" for some of its USB DVD/BluRay drives which you can (but don't have to) set for playing music CDs; if you switch it off the drive spins noticeably faster when playing (not ripping!) music CDs and becomes noticeably more noisy.

Also:

https://www.audiosciencereview.com/...-players-make-audible-mechanical-noise.34525/

EDIT: Re. the actual noise. Below is video demo-ing the noise badly centered disks make. This is just above the frequency of rattle my SONY DVD player used to make when playing music CDs (before I fixed it, aside from the other mechanism noises the drawer also rattled). Which to me indicates the SONY is spinning music CDs at some 4000rpm perhaps, not a maximum 500rpm (at 500 rpm there is no way you would get a rattle like that at some 60-70Hz):

 

[Davesrose]

Could it be that these oddballs are following an ancient and obsolete red book standard? I think there was an update to allow more than 72 minutes on a disc, and reports of firmware fixes would tend to indicate a missing update.

Standard redbook was up to 74 minutes. With varying print technologies, audio CDs got over 79 minutes (CD players that weren't compatible would just cut off at the last track).

Maybe you can find some verification that CDs are played differently. Everything I found said that CDs and DVDs play with constant linear velocity.

I think there may be some new players that treat discs as CD-ROM (or DVD/BD). I think the issue may be most optical players now being designed around data ROM standards (where data is stored as segments) vs the old CD audio standard of the data being a linear spiral. It's more about the file system....and that current manufacturing for a CD player will dictate a CD-ROM drive and PCB that supports other audio formats on an optical data disc.

RE noise with optical player....I admit the main optical player I use regularly now is a high end Panasonic UHD player for 4K movies. I think it's pretty quiet when it's loading a movie....but once the movie starts, whatever noise it could emit is drowned out by my speakers. If I did have to look at all the optical players I've had....maybe my dedicated high end SACD player might be the loudest: it has a noticeable fan noise (but still pretty minimal as it's much better with classical music compared to a record player).

 

[2leftears]

I think there may be some new players that treat discs as CD-ROM (or DVD/BD). I think the issue may be most optical players now being designed around data ROM standards (where data is stored as segments) vs the old CD audio standard of the data being a linear spiral. It's more about the file system....and that current manufacturing for a CD player will dictate a CD-ROM drive and PCB that supports other audio formats on an optical data disc.

Like you suggest, I also suspect it is because the drives in some players are primarily designed as BluRay/DVD/CD-R drives, with CD-DA support as an extra feature rather than having been optimised for it.

Data disks do still store data in a spiral though, it isn't like concentric segments on a HDD. I also used to think that until it dawned on me that if data disks used concentric segments then burning CD-DA format spiral data to a disk would be impossible (or regular CD players wouldn't be able to read it), so I looked it up:

On data disks (CD-ROM/CD-R) there is a spiral called the 'pre-groove' molded into the polycarbonate to guide the laser, the data is written in a dye layer just in front of it. Low-level data format with EFM (Eight-to-Fourteen Modulation), CIRC (Cross-Interleaved Reed-Solomon Code) are inherited from (and compatible with) the red-book specs for CD-DA music disks, but the higher-level data format is specified in the yellow-book specs for CD-ROM disks. Whilst the same at the low data level, for CD-DA the data 'blocks' are called 'timecode frames' whereas for the CD-ROM the same 'blocks' are called 'sectors'.

Relevant info:

CD-R physical characteristics: https://en.wikipedia.org/wiki/CD-R#Physical_characteristics
timecode frames: https://en.wikipedia.org/wiki/Compact_Disc_Digital_Audio#Frames_and_timecode_frames
CD physical details general info: https://en.wikipedia.org/wiki/Compact_disc#Physical_details

From the first link:

The polycarbonate disc contains a spiral groove, called the pregroove because it is molded in before data are written to the disc; it guides the laser beam upon writing and reading information. The pregroove is molded into the top side of the polycarbonate disc, where the pits and lands would be molded if it were a pressed, nonrecordable Red Book CD. The bottom side, which faces the laser beam in the player or drive, is flat and smooth. The polycarbonate disc is coated on the pregroove side with a very thin layer of organic dye. Then, on top of the dye is coated a thin, reflecting layer of silver, a silver alloy, or gold. Finally, a protective coating of a photo-polymerizable lacquer is applied on top of the metal reflector and cured with UV light.

This, from the third link, is a controversial bit IMO:

When playing an audio CD, a motor within the CD player spins the disc to a scanning velocity of 1.2–1.4 m/s (constant linear velocity, CLV)—equivalent to approximately 500 RPM at the inside of the disc, and approximately 200 RPM at the outside edge.[76] The track on the CD begins at the inside and spirals outward so a disc played from beginning to end slows its rotation rate during playback.

This was entirely consistent with how I experienced (and saw) CD players play back music CDs until some 15 years ago or so; since then I have come across a growing number of players that behaved entirely inconsistent with that information and spin not only data CDs (expected) but also normal music CDs (CD-DA) at much faster speeds of sometimes several thousand RPM (that was entirely unexpected behaviour, but beyond doubt, I have seen it myself and still have one of those players). I have in fact returned a CD player for that precise reason (a late generation SONY DiscMan some years ago). With DVD and BluRay players and cheap radio/CD players I can live with that 'flaw' (noisy) as I normally don't use them to play music CDs and the drive noise doesn't bother me nearly as much when watching movies as it does when listening to music.

 

[bigshot]

I wonder why there is no mention of DVD players that treat CDs as data discs. I would think that if a DVD player that was like that existed, 1) there would be a name for the “feature” used on spec sheets and advertising; and 2) someone would be posting that with this kind of player, the veil had been lifted and their soundstage widened.

 

[2leftears]

I wonder why there is no mention of DVD players that treat CDs as data discs. I would think that if a DVD player that was like that existed, 1) there would be a name for the “feature” used on spec sheets and advertising; and 2) someone would be posting that with this kind of player, the veil had been lifted and their soundstage widened.

I'm not sure there would be a marketing opportunity here (but some audiophiles might disagree as you suggest).

At the lower-level data format music CDs are no different to data disks. Same 'block' sizes, same low-level red-book data structure incl. EFM & CIRC.

The difference is the higher-level interpretation what that data encodes, incl. an extra level of error correction for data disks as specified in the yellow book. Once the lower-level data has been demodulated and de-interleaved, in theory it is entirely up to the drive manufacturers how they decide to store/buffer/stream that data depending on use (direct playback of PCM music data, data for a ripping program, general data over a bulk USB data transfer, etc).

On old(-style) CD players the low-level red-book standard data is read at approx. the speed at which it is needed for CD playback, hence only a small buffer is required for minor variations in disk-speed (and control thereof) and de-interleaving of the data, prior to sending it to the filter for oversampling (and S/PDIF out) and then onto the DAC.

But it doesn't have to be. The disk can be run at higher speed; since each timecode frame is uniquely identified they can be read fast in intermittent chunks, appropriately matched up and stored in a bigger buffer for de-interlacing, prior to either sending out as an S/PDIF stream for direct playback, or packaging up as a bulk data transfer for ripping music data or non-music data for computers.
It is entirely feasible that for doing so manufacturers would prefer to use the same data storage logic used for reading data disks, and you end up with a fast spinning intermittently read disk even though the PCM data still comes out of the drive at the correct rate for the DAC to do direct playback of a music CD.

I can speculate that another reason might be limitations on the PLLs they use in the drive. In a mechanism that has been optimised to cater for 48x reading/writing speed maybe some PLL circuitry would struggle to lock onto the EFM data at a read speed as low as 1x; too much DC drift then if optimised for very high reading speeds so maybe that is why some drives only seem to offer read speeds of 4x or higher even for music CDs.

 

[XTF1]

I'm not sure there would be a marketing opportunity here (but some audiophiles might disagree as you suggest).

At the lower-level data format music CDs are no different to data disks. Same 'block' sizes, same low-level red-book data structure incl. EFM & CIRC.

The difference is the higher-level interpretation what that data encodes, incl. an extra level of error correction for data disks as specified in the yellow book. Once the lower-level data has been demodulated and de-interleaved, in theory it is entirely up to the drive manufacturers how they decide to store/buffer/stream that data depending on use (direct playback of PCM music data, data for a ripping program, general data over a bulk USB data transfer, etc).

On old(-style) CD players the low-level red-book standard data is read at approx. the speed at which it is needed for CD playback, hence only a small buffer is required for minor variations in disk-speed (and control thereof) and de-interleaving of the data, prior to sending it to the filter for oversampling (and S/PDIF out) and then onto the DAC.

But it doesn't have to be. The disk can be run at higher speed; since each timecode frame is uniquely identified they can be read fast in intermittent chunks, appropriately matched up and stored in a bigger buffer for de-interlacing, prior to either sending out as an S/PDIF stream for direct playback, or packaging up as a bulk data transfer for ripping music data or non-music data for computers.
It is entirely feasible that for doing so manufacturers would prefer to use the same data storage logic used for reading data disks, and you end up with a fast spinning intermittently read disk even though the PCM data still comes out of the drive at the correct rate for the DAC to do direct playback of a music CD.

I can speculate that another reason might be limitations on the PLLs they use in the drive. In a mechanism that has been optimised to cater for 48x reading/writing speed maybe some PLL circuitry would struggle to lock onto the EFM data at a read speed as low as 1x; too much DC drift then if optimised for very high reading speeds so maybe that is why some drives only seem to offer read speeds of 4x or higher even for music CDs.

Mentioned in a previous post: is this about lack of support for DAO (disk at once) vs. TAO (track at once) modes?

 

[2leftears]

Mentioned in a previous post: is this about lack of support for DAO (disk at once) vs. TAO (track at once) modes?

No, different issue (I think); the "gapless" issue mentioned pertains to shop-bought pressed music CD playback on (supposedly) 'normal' Audio CD players.

EDIT: the discussion then diverted to one about drive noise and disk spin speeds.

 

[bigshot]

Is there any documentation of which DVD drives behave like this? I bet it’s a tiny percentage like the players that couldn’t do gapless.

I think we end up spending 99% of our time talking about 1% of equipment. This is the “ultra rare exceptions to the rule forum”. As I always say, if I bought something like this and it was noisy, I’d send it back for a refund.

I have a half dozen players of all kinds here and none of them make noise. I can recommend model numbers that are silent if anyone needs a new player.

 

[2leftears]

I think we end up spending 99% of our time talking about 1% of equipment. This is the “ultra rare exceptions to the rule forum”. As I always say, if I bought something like this and it was noisy, I’d send it back for a refund.

I have a half dozen players of all kinds here and none of them make noise. I can recommend model numbers that are silent if anyone needs a new player.

Well, arguably only 1% or less of the equipment is interesting; little point asking about the quirks of the majority of equipment that behaves as expected (or as desired)...

On the other hand; I haven't personally heard a quiet DVD player yet; most environments I encounter them in are too noisy to judge it. Maybe the vast majority are quiet; I wouldn't know until I can try them at home myself.

But the reason I posted this wasn't to have a moan (I don't regularly play CDs on my own DVD or BluRay players, I use my CD players for that). Rather I was simply curious from a technological/engineering point of view; I'm an engineer and these curious technical details are interesting to me but I don't have the means to access the required (sometimes proprietary) data, and was merely wondering if anyone else here had already noticed/read about the same and/or knew about the technical details behind this type of player behaviour.
I know how old-school 80's & early 90's CD players read & process the CD data, hence re. CD spin rates I immediately noticed that some more recent players (DVD players included) were doing it different by design (not resulting from a fault), and different from what the general CD-related information on e.g. Wikipedia suggests. This piqued my curiosity...

 

[Davesrose]

Data disks do still store data in a spiral though, it isn't like concentric segments on a HDD. I also used to think that until it dawned on me that if data disks used concentric segments then burning CD-DA format spiral data to a disk would be impossible (or regular CD players wouldn't be able to read it), so I looked it up:

I said that the file system format is different (not that ROM disks are concentric circles). The way the data is stored as segments means the laser assembly accesses areas of the disc differently than an audio CD.