I need: "cheap hardware decoder" safe CBR settings

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I need: "cheap hardware decoder" safe CBR settings

2003-02-02 06:21:57

Hi all LAME gurus,

I have left extreme lurker mode to ask pose some questions....

I've found that many DVD players and other "MP3-CD compatible" devices use hardware decoders that will not play VBR and/or high bitrate files properly.

Some players play VBR as if the whole file is at the initial bitrate (which makes the songs play very fast because the early frames are invariably a low bitrate), while others play VBR at the correct speed but decoding errors appear because the decoder in question cannot handle higher than say 256 kbps (maybe because of a playback memory buffer that is too small??? - companies saving on cost, etc.). Other players refuse point blank to play VBR.

Such problems are rarely documented in the manual of the hardware, and sales staff invariably have no clue of what you are going on about when you ask them. Also - many stores will not let you test hardware with your own CD. Thus it is not always possible to find out until too late if the player supports files correctly. It is a pain to have to return hardware (especially when it is not obvious to the sales staff what the problem with it is!) but missing out on a bargain DVD player is not fun either!

This has led me to be disenchanted with "alt preset standard" and VBR in general, despite having encoded lots of stuffa large portion of my CD collection with APS. I know of course that for quality VBR is the way to go. However CBR (for some pathetic reason) seems to be much more widely supported by hardware decoders, and I have decided to go with CBR from now on (I can hear all those purists amongst you gasp).

I never want to re-encode my collection again!!!!!!!!!!!!! (yes this many exclamation marks are required). I want to be able to buy any mp3 hardware and have it be able to play the files. I also want the files to sound OK on a low to medium quality HiFi system.

Therefore, while I know I asking for a bit much here...

I need to know the ideal way to get the best sounding CBR LAME MP3's. I'll be going for 160 or 192 kbps . These bitrates will ensure that the cheapest hardware MP3 players can handle the files (including those with limited memory buffer concerns), while also ensuring a decent sound quality.

I think the following issues need to be addressed for this topic:

- what low pass frequency should be used to ensure best sounding overall audio for 160/192 CBR?
- do any hardware decoders have problems with joint stereo?
- do any hardware decoders have problems when flipping between stereo and joint stereo (nssafejoint)? i.e. could using the "alt preset CBR" settings cause problems for the hardware?
- is it necessary to normalize PRIOR to ENCODING to reduce clipping anomalies?
- any other issues that might be important

thanks and I hope you can help.

RD.

I need: "cheap hardware decoder" safe CBR settings

Reply #1 – 2003-02-02 07:25:25

Quote

- what low pass frequency should be used to ensure best sounding overall audio for 160/192 CBR?

don't specify your own lowpass, just use the lowpass preconfigured in the --alt-preset xxx cbr switch

Quote

- do any hardware decoders have problems with joint stereo?

I doubt it, seeing as the vast majority of encoders (even bad ones) default to joint stereo afaik.

Quote

- do any hardware decoders have problems when flipping between stereo and joint stereo (nssafejoint)? i.e. could using the "alt preset CBR" settings cause problems for the hardware?

Not sure exactly what you mean, but I don't think the cbr presets have been known to cause any problems.

Quote

- is it necessary to normalize PRIOR to ENCODING to reduce clipping anomalies?

No. Use mp3gain on the mp3's after encoding to equalize volumes across tracks and/or eliminate clipping. It modifies the mp3's global gain, which should be supported by all hardware decoders (works on my portable)

Personally I'd just put the effort in to get a good hardware decoder (you don't mention if you are looking for a portable, dvd player or other), and use your vbr files, rather than trying to get acceptable quality out of cbr.

I need: "cheap hardware decoder" safe CBR settings

Reply #2 – 2003-02-02 07:44:10

I have a kenwood portable which plays VBR well. However I just bought a VOXSON DVD250 DVD player, and it doesn't handle VBR at all well. It plays the files at the correct speed but the decoder screws up the sound. The files were encoded with "alt preset standard".

CBR files with 256 kbps and lower play much better with the DVD player. 320 kbps plays with the same errors as VBR so I guess that the decoder can't handle 320 kbps too well (which would explain the trouble with APS). I hear occasional glitches with 256 but the lower modes have no glitches.

I know you'll tell me to encode with 256 kbps CBR, or VBR with a 256 kbps upper limit but I'd rather encode it in a format which will play anywhere in any player - and in any future player that I may buy.

The DVD player is great otherwise - it also plays MPEG files and JPG files. It was also only $178 here in Australia (~$100 in US dollars).

thanks,
RD.

I need: "cheap hardware decoder" safe CBR settings

Reply #3 – 2003-02-02 08:42:16

I"d say go for --alt-preset cbr 192 and MP3Gain the files afterwards. That should work on every player on this planet and sound quite good...

I need: "cheap hardware decoder" safe CBR settings

Reply #4 – 2003-02-02 09:33:18

I would add the following caveat to what's already been suggested: At least one DVD-based MP3 player I've seen had problems with the L.A.M.E./Xing tag. I have no idea why (Dibrom, Gabriel or any of the others, is there a simple explanation for this?), but on the off-chance that it could affect playback in whatever unit you wind up using you might also want to disable the tags with the "-t" switch. So your command-line would look like this: --alt-preset cbr 192 -t

For the record, I can't remember the name of the troublesome DVD player. I saw it about a year and a half ago, give or take a few months; the front plate was roughly 4 x 12 inches, and silver with white buttons. As I recall, it only played MPEG-1 Layer-III (not MPEG-2 Layer-III, which made it useless for Old Time Radio programs), and I think the minimum supported bitrate may have been 56kbps. Does anyone know what this model was?

- M.

I need: "cheap hardware decoder" safe CBR settings

Reply #5 – 2003-02-03 11:59:03

Thanks for the info folks.

M - I had never heard of that -t option before. What does it have for the tag when -t is used? I presume the tag is in a part of the file that is skipped by the decoder?? My knowledge of mp3 file construction is quite limited I admit.

While on this subject - is there a website out there with a run-down of the mp3 file anatomy? An "Mp3 file construction for dummies" so to speak...?

Someone's sure to say RTFM...

RD.

I need: "cheap hardware decoder" safe CBR settings

Reply #6 – 2003-02-04 12:33:44

It is NOT acceptable to pay money for a so called "DVD/MP3"-Player, which does NOT play Lame/MP3 with 320 kbit/s, or VBR.

Return it, no problem.

Just tell them, the player does not support the mp3 specs, which include 320 kbit and VBR.

No problem for you, to show them the faults, take your VBR songs.

So, there are meanwhile a lot of good recommended DVD/SVCD/MP3-players out there for only 100 € or $.

Try

Cyberhome 505 or similar,

or:

SEG Los Angeles and related,

last but not least:

TYT2000 & clones

I need: "cheap hardware decoder" safe CBR settings

Reply #7 – 2003-02-04 20:13:59

Yeah, I agree with that. I didn't post anything in that way for the sake of not looking like the old moaner (I've run out of "moaning quota" after Atlantis' thread ), but now that you've said it... I personally wouldn't put up with those limitations either.

I need: "cheap hardware decoder" safe CBR settings

Reply #8 – 2003-02-09 09:43:27

I use MP3 as a format which allows me to fit many songs onto a CD. I want those songs to be compatible with all MP3 playing equipment (that's why I chose CBR). I did not choose MP3 because it has the ultimate quality - I would stick to CD for that. The MP3's would be played mostly on public transport, etc. There you have my reasons.

For those who give a stuff, here's how I solved my tradeoff between quality and compatibility:

I chose 192 kbps Joint-Stereo CBR for compatibility reasons.
However I decided to use my own lowpass (rather than the defaulted one), because it is my ears that will be doing the listening. Also a lower lowpass will let the other frequencies sound better because there are more bits devoted to them by the MP3 encoder.

First I decided to test my high frequency hearing using CoolEdit Pro. I grapped Radiohead's OK Computer onto my HDD. Then I chose some songs and did some high-passes on them, leaving only frequencies above a certain threshold. I found I could hear the sounds below 16 kHz but any high passes above this led to frequencies I could not hear. You could see them in frequency view in CEPro (and there was a fair bit there) but I could not hear anything during playback. I'll leave that to the domestic pets of the world

With this in mind I eventually chose a lowpass of 16500 Hz with 1500 Hz cutoff range (the reduction in dB starts at 16500 dB and increases up to 18000 dB, above which the frequencies are silenced). Apparently unwanted distortion can occur if the dropoff occurs in a too narrow range (i.e. if the frequencies above the lowpass frequency are set at zero volume, starting immediately above it).

I found that this lowpass led to WAV files that sound just perfect to my ears. I do not own extremely expensive speakers but I won't be carrying such with me on the train anyway.

I made a script in CEPro to do the lowpass on a selection of WAVs in one go using the batch processing option.

Now in LAME I disabled the adaptive lowpass function and simply used the following commandline (To avoid clipping issues I use MP3Gain):

-b 192 -m j -h -k

After encoding I could not detect any audible anomalies with the MP3's.

I hope anyone here with similar issues may be helped by this.

RD.

P.S.... Just as a side project I decided to check how --alt-preset standard would treat my lowpassed WAVs compared to the same tracks non-lowpassed. I did not disable the adaptive lowpass in the preset and found that the (previously) lowpassed files were ~30-40 kbps smaller. I could not tell the difference in sound. Really I think people should check their own hearing (well - also any other people that want to listen to the particular MP3 file) when they want to get the smallest file size from the VBR presets.

RD.

I need: "cheap hardware decoder" safe CBR settings

Reply #9 – 2003-02-09 10:11:43

Quote

First I decided to test my high frequency hearing ...

FYI: KikeG provided something similar some months ago. He found an example of real music with audible high frequency content suitable very well for this purpose IMO. The HA thread is How high can you hear (with music & lowpass), ABX required.

I need: "cheap hardware decoder" safe CBR settings

Reply #10 – 2003-02-09 18:25:04

RD, if you ever do come across any anomalies with your default settings outlined at the bottom of your last post, I suggest you try --alt-preset cbr 192 -k -t instead.

I need: "cheap hardware decoder" safe CBR settings

Reply #11 – 2003-02-11 07:21:16

Shadow RD

There are many fine DVD/MP3 players available in Australia now for around $200. By now, many or most of them should handle 320 kbps and VBR. In particular, look for clearance specials on discontinued models by the likes of Sony, Panasonic, Pioneer, etc.

Nevertheless, if you want guaranteed MP3 compatibility on virtually any MP3 player, encode with 160 kbps CBR.

Frankly, my 53 year-old ears cannot tell the difference between the original CD and files encoded with LAME 3.90.2 --alt-preset cbr 160 (played on my good quality hi-fi system using a Pioneer DVD/MP3 player).

I suspect this is about the best quality you can get at 160 kbps, so I recommend just using this setting (or cbr 192 if you must) and don't play with other settings. You'll squeeze about 8 hours of music onto an 80 minute CD and I guarantee it will sound fine on the bus or train!

I went through the stage of trying to select the best LAME settings for the best sound, but now realise this is sheer folly and none of my settings at a given bitrate are likely to equal or better the LAME --alt-preset settings (using 3.90.2 or 3.91 that is).

Regards
DrD

I need: "cheap hardware decoder" safe CBR settings

Reply #12 – 2003-02-11 08:53:02

Quote

Now in LAME I disabled the adaptive lowpass function

LAME has an adaptive lowpass?

Hehe, you might want to check into that further. I recall Dibrom pointing out the absence of that as one of the problems facing the LAME project.

Perhaps you mean regular x-pass filters? Though if I recall it takes a switch to enable them, except in the case of the presets. If I'm wrong, someone feel free to correct me. B)

BTW, welcome to the forum.

I need: "cheap hardware decoder" safe CBR settings

Reply #13 – 2003-02-12 09:57:14

mpcfiend,

fair enough. I was just describing what was in the razorlame log. Something about -k "stopping the adaptive lowpass function". I think that is actually what it says. At 192 kbps CBR the lowpass is set to a small range of frequencies ~19200-19500 Hz which is way to high for my purposes. Perhaps the "adaptive lowpass" in the LAME "text output" simply means that for different CBR bitrates LAME chooses a different lowpass frequency cutoff.

The (lack of an) adaptive lowpass you are talking about in LAME must refer to VBR. I presume that you can't (with LAME) choose a different lowpass for each and every frame. Maybe when you change the lowpass in every frame too much distortion is caused - some sounds would span more than one frame and if the lowpass frequency changes perhaps some type of audible distortion could occur. I could be wrong...

anyway, here's what the LAME html file says about -k:

* -k full bandwidth
Tells the encoder to use full bandwidth and to disable all filters. By default, the encoder uses some highpass filtering at low bitrates, in order to keep a good quality by giving more bits to more important frequencies.
Increasing the bandwidth from the default setting might produce ringing artefacts at low bitrates. Use with care!

RD.

I need: "cheap hardware decoder" safe CBR settings

Reply #14 – 2003-02-12 12:10:42

There is another way of looking at this issue...

There is at least one buggy "mp3" decoding chip out there which has problems above 192kbps. It's quite an early one, and I would imagine that it's quite cheap. There are also lots of other, more recent chips which decode perfectly.

There is no reason for manufacturers to use this old chip now. Existing (unwanted) supplies must make it very cheap, but then some of the cheapest players are able to decode perfectly. So, it's either ignorance, or penny pinching that causes this chip to be used in any current player.

The solution? Return the defective player to the shop. This send the right message to the manufacturers, and may make them take notice. Otherwise, as long as they can still sell "mp3" players that don't play mp3 properly, they'll use up stocks of this terrible chip.

Selling an mp3 player that has problems above 192kbps is like selling an FM radio that won't tune above 100MHz!

Cheers,
David.

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