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Topic: mp2 to mp3 (Read 7564 times) previous topic - next topic
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mp2 to mp3

A friend is recording audio from a satellite (I think so anyway) streamed broadcast.

The audio's lifecycle goes like this:

Quote
ts (transport stream) -> AIFF -> MP3

Demuxing of the transport stream is now set to 'low level' in the program MPEG Streamclip.
After that he uses Quicktime 7 to chop off excess data from the Aiff's that are produced. The transport streams are 48 khz 16 bit so he just leave thems at that when exporting from QT.

He then uses version 0.7.4-3 of a program called normalize, to uh... normalize the files.

LAME 3.96.1 --preset extreme -vbr-new is used to encode them.


I have some thoughts on this, but bet you guys and girls have much better ones  on this process... and any better alternatives.

Much appreciated.

jb

mp2 to mp3

Reply #1 –
I have two questions instead of an answer. 

Why does your friend convert the streams from mp2 to mp3? (transcoding from lossy to lossy codec reduces quality)

If it is really required to transcode to mp3 (for a portable player, maybe?), then why waste disk space using "--preset extreme"? (use "--preset standard" or even something lower)

mp2 to mp3

Reply #2 –
Quote
I have two questions instead of an answer. 

Why does your friend convert the streams from mp2 to mp3? (transcoding from lossy to lossy codec reduces quality)
[a href="index.php?act=findpost&pid=296515"][{POST_SNAPBACK}][/a]

Because the music file is then made available for members of his website to download and listen to - they'll want it as an mp3 file

Quote
If it is really required to transcode to mp3 (for a portable player, maybe?), then why waste disk space using "--preset extreme"? (use "--preset standard" or even something lower)
[a href="index.php?act=findpost&pid=296515"][{POST_SNAPBACK}][/a]

I agree with what you're saying and have no issue with this, but I'm not gonna change his mind on this.  The members of the website will also want the best quality possible from a LAME encoded mp3 file (without using the insane preset), so I'm ok with the extreme setting.

I guess what I'm trying to establish is the best way for him to get the best quality files from this stream to his members.  We all know that going from lossy to lossy isn't good... indeed he's frigging normalizing the file which I'd rather he didn't.  When I go back to him I want to give him the best possible advice on how to achieve the best outcome.

If you want/need more info about the setup etc just let me know and I'll get it from him.

Thanks

mp2 to mp3

Reply #4 –
OK, if he *must* use transcoding, why not use wavegain? It's better than normalization when it comes to volume control.

Why not use --preset fast extreme? It's easier to type, and easier to recognize.

mp2 to mp3

Reply #5 –
Quote
OK, if he *must* use transcoding, why not use wavegain? It's better than normalization when it comes to volume control.
[a href="index.php?act=findpost&pid=296520"][{POST_SNAPBACK}][/a]

WaveGain - yep I thought that too.
Quote
Why not use --preset fast extreme? It's easier to type, and easier to recognize.
[a href="index.php?act=findpost&pid=296520"][{POST_SNAPBACK}][/a]

That's maybe me just getting it wrong - I think he does use the --preset fast extreme setting.

Thanks for the feedback.

mp2 to mp3

Reply #6 –
Quote
Because the music file is then made available for members of his website to download and listen to - they'll want it as an mp3 file
[...]
The members of the website will also want the best quality possible from a LAME encoded mp3 file (without using the insane preset), so I'm ok with the extreme setting.

IMO, these two things don't match. The members of the website say they want the best reduced-quality files they can get? 

I strongly agree with kjoonlee that the original mp2 streams would be the best choice. (no transcoding/normalizing at all)

mp2 to mp3

Reply #7 –
Right, ok.

It's a live recording of a 2hr BBC show.  This is then available to d/l by members (I'm one of those members and so have no involvement in this process at all) from a website (I'm sure the Beeb know about the site and are not bothered - the site's been around for a while now).  In between that 'capture' and 'make available for d/l' is what I'm interested in / worried about.

I don't have satellite recording capabilities and have never used mp2 files. 

I agree that it's best to not transcode between lossy codecs where possible.  However, there will have to be some manipulation of the file because it's highly likely that a few seconds (maybe minutes or hours) before and after the show would have to be removed.  Sure there are programs that can do that without decoding like mp3DirectCut and mp3splt.

When I say the members will want the best quality possible from an mp3 file I'm second guessing them, but I'm sure it's true.  Whether any of them would've heard of mp2 I don't know -  and this could cause them to start getting worried etc etc.  I'm sure many of us audiophiles know what it's like trying to convince people about the 'best' way to do things with audio etc etc.
 
So, it seems that capturing the audio via a satellite stream as mp2 (is this the format that is actually being sent?), using some non-destructive audio editor to remove unwanted sections, and then applying mp3gain (replaygain probably better but less software support) seems the best approach (and then probably changing .mp2 to .mp3 so as not to scare the members??).  Would this be correct?

Thanks
Scott

mp2 to mp3

Reply #8 –
I don't think mp3gain will work with MP2 files. But come to think of it, what you hear on the radio is probably already dynamically compressed; there should be no need to alter the volume further.

mp2 to mp3

Reply #9 –
Ok, so I've been doing some reading about this stuff as it's new to me.  Does this sound like the best option:

(1) The Transport Stream (using DVB-S) is captured by a program - recommendations?

(2a) The file is demuxed to split the file into the relevant data streams - is this necessary with a broadcast from the BBC?  or is that dependent on what is being streamed?  I mean, there's no video is this stream, what else could there be? - digital data such as the program name?
or
(2b) The file is converted to mp2 from the PVA captured format using a program like PVAStrumento (as recommended here).

(3) Use a non-destructive audio editor that supports mp2 (like mp3DirectCut [can BeSlice do this?]) to remove unwanted sections of the file - in this instance the beginning and end sections (outside of the actual show).

(4) Then use BeSplit to 'normalise' the files: HA threads here, here and here all refer.

(5) File is now ready for tagging - mp2s can be tagged right? (I'm at work and cannot test)

Now, if the file is left as mp2 what's the compatibility like for software apps and portable players alike?  Can it simply be renamed to 'mp3'?

Your help is, as always, greatly appreciated.

Scott

mp2 to mp3

Reply #10 –
Quote
Ok, so I've been doing some reading about this stuff as it's new to me.  Does this sound like the best option:

(1) The Transport Stream (using DVB-S) is captured by a program - recommendations?

(2a) The file is demuxed to split the file into the relevant data streams - is this necessary with a broadcast from the BBC?  or is that dependent on what is being streamed?  I mean, there's no video is this stream, what else could there be? - digital data such as the program name?
or
(2b) The file is converted to mp2 from the PVA captured format using a program like PVAStrumento (as recommended here).

(3) Use a non-destructive audio editor that supports mp2 (like mp3DirectCut [can BeSlice do this?]) to remove unwanted sections of the file - in this instance the beginning and end sections (outside of the actual show).

(4) Then use BeSplit to 'normalise' the files: HA threads here, here and here all refer.

(5) File is now ready for tagging - mp2s can be tagged right? (I'm at work and cannot test)

Now, if the file is left as mp2 what's the compatibility like for software apps and portable players alike?  Can it simply be renamed to 'mp3'?

Your help is, as always, greatly appreciated.

Scott
[a href="index.php?act=findpost&pid=296546"][{POST_SNAPBACK}][/a]


I record a lot of radio from Freeview and you've described what I usually do except:

(2b) I prefer ProjectX because it will tell you if there were any errors in the stream when you demux.

(4) I find that if I decode a besplit normalized mp2 file it often clips so I never use it. If you are recording from R1, R2, 1Xtra or 6Music it will already be very loud and you'll only get 2-3db of gain if you normalize anyway.

(5) Yes but WMP doesn't read them.

Software support for mp2 is generally very good. I would not worry about people downloading mp2 files and being unable to play them.

Quote
Can it simply be renamed to 'mp3'?


No, mp2 is not mp3. Although renaming to mp3 can allow you to play mp2 files on some hardware players, it doesn't work for all of them, and is not needed for others as they will play mp2 files with the correct extension.

If you can't convince people of the merits of keeping the original mp2 files convert them to real mp3 files instead. If you rename them people are likely to find out eventually and they probably won't be very happy when they do.

mp2 to mp3

Reply #11 –
Quote
I record a lot of radio from Freeview and you've described what I usually do except:

(2b) I prefer ProjectX because it will tell you if there were any errors in the stream when you demux.

(4) I find that if I decode a besplit normalized mp2 file it often clips so I never use it. If you are recording from R1, R2, 1Xtra or 6Music it will already be very loud and you'll only get 2-3db of gain if you normalize anyway.

(5) Yes but WMP doesn't read them.

Software support for mp2 is generally very good. I would not worry about people downloading mp2 files and being unable to play them.

Quote
Can it simply be renamed to 'mp3'?


No, mp2 is not mp3. Although renaming to mp3 can allow you to play mp2 files on some hardware players, it doesn't work for all of them, and is not needed for others as they will play mp2 files with the correct extension.

If you can't convince people of the merits of keeping the original mp2 files convert them to real mp3 files instead. If you rename them people are likely to find out eventually and they probably won't be very happy when they do.
[{POST_SNAPBACK}][/a]

Many thanks benc, just what I was looking for.

So, if step (4) above was left out then the procedure should be sorted? --> get the TS file, demux it into mp2 (which is a lossless process right?), remove some unwanted data, add tags and voilà: left with an mp2 file that hasn't been decoded and then encoded (again) using LAME into mp3.

However, what if some of the original captured recordings suffer clipping?  Can normalisation be used on the TS file to reduce the sound level?

To add to the complexity my friend has a Mac (using OS X 10.4 Tiger), so will the programs like ProjectX etc work?  For example, mp3DirectCut doesn't appear to be compatible with Macs - but [a href="http://mp3splt.sourceforge.net/]mp3splt[/url] is.

mp2 to mp3

Reply #12 –
Quote
So, if step (4) above was left out then the procedure should be sorted? --> get the TS file, demux it into mp2 (which is a lossless process right?), remove some unwanted data, add tags and voilà: left with an mp2 file that hasn't been decoded and then encoded (again) using LAME into mp3.


Yes.

Quote
However, what if some of the original captured recordings suffer clipping?  Can normalisation be used on the TS file to reduce the sound level?


Loweing the level won't removing clipping if it's already clipped. Anyway besplit only lets you normalize, you can't use it to raise or lower the volume by x db (well I've never been able to get it to do that) and I don't know of any other app that lets you change the volume of mp2 files.

Quote
To add to the complexity my friend has a Mac (using OS X 10.4 Tiger), so will the programs like ProjectX etc work?  For example, mp3DirectCut doesn't appear to be compatible with Macs - but mp3splt is.
[a href="index.php?act=findpost&pid=296623"][{POST_SNAPBACK}][/a]


ProjectX use Java so I'm assuming it will work on OS X if you have a Java VM installed. I've never used OS X so I don't know what tools are avalible. As far as I know Besplit is win32 only.

mp2 to mp3

Reply #13 –
When transcoding an mp2 file to mp3 using LAME, is the following in the correct order:

Code: [Select]
--preset fast extreme  --mp2input infile.mp2
i.e. should the '--mp2input' switch be after the preset switch?

Does LAME decode the mp2 to then re-encode to mp3? or does it simply encode the mp2 to mp3?
Would there be any difference in the resulting LAME mp3 if the mp2 was decoded to wav and then encoded to mp3 or simply transcoded to mp3 from mp2?

So many questions this morning! 

mp2 to mp3

Reply #14 –
Quote
Quote
Can it simply be renamed to 'mp3'?


No, mp2 is not mp3. Although renaming to mp3 can allow you to play mp2 files on some hardware players, it doesn't work for all of them, and is not needed for others as they will play mp2 files with the correct extension.

If you can't convince people of the merits of keeping the original mp2 files convert them to real mp3 files instead. If you rename them people are likely to find out eventually and they probably won't be very happy when they do.
[a href="index.php?act=findpost&pid=296593"][{POST_SNAPBACK}][/a]


That all true - but they're getting an illegal copy for free. ("The BBC obviously don't mind because they haven't stopped us" is irrelevant in terms of the legality or otherwise of reproducing copyright material). Hence, the people who download these files have no right to moan, whatever the "provider" decides to do!

I'd go with jaybee's process, and I _would_ rename it to mp3 (and tell people that that is what I have done, and not to worry about it unless it causes problems!). It'll save a lot of questions and confusion for simple users, and it'll be obvious what has happened to advanced users (because Winamp and mp3gain will tell them if they care to look/try!). It'll annoy some people when certain players don't play the files - but compliant mp3 players _do_ player mp2-as-mp3 files - and there are plenty of players out there that will only see/play mp2 files when renamed to mp3. (There were plenty of non-compliant players that choked on VBR - does that stop you from using it?)


What's more, 192kbps mp2 is hardly very high bitrate or quality for an encoding source. You're not helping the sound quality by transcoding, and I'd bet you're actually increasing the bitrate using those settings!

The simple solution is to offer the original mp2 for download - use the extension mp2 or mp3 as you wish - and put simple explanations on the website - even provide a link to lame and a suggested command line to transcode people want to. Then everyone has a choice.

Cheers,
David.