Relationship between loudness (volume level??) and Sound Quality

[cmr_for3]

Dear all,

Thought I would ask here as you seem a knowledge bunch when it comes to Audio related matters. I'm not an Audiophile but do have some nice kit so thought I best start using to best effect (To give you an idea during this process I've learnt that aac is superior to mp3)

So with some Christmas Amazon vouchers I bought myself a Humax FVP 5000 purely for recording radio (I now record SD stuff as well) and chose this model because you can transfer these recordings to your PC's harddrive unencrypted. Essentially what is recorded is an NTS which once transferred is actually an MPEG 2 file (this is how I understand it) I then have to encode this to MP3 to get it to work. This strange thing is , is that a group of files I've been listening to encoded it would seem at 120kbps are much louder than these mp3s at 192kbps.

What gives?

many thanks

[Dave2002]

I do that from Freesat - and I don't think there are any major problems. In the past I have also done that from Freeview. Indeeed, I'm not aware of needing to convert mp2 to mp3 any more - maybe the software I use sorts this out. I do vaguely remember having to do that in the past. What are you using to do the conversion? Maybe that software is changing the volume levels.

[cmr_for3]

I do that from Freesat - and I don't think there are any major problems. In the past I have also done that from Freeview. Indeeed, I'm not aware of needing to convert mp2 to mp3 any more - maybe the software I use sorts this out. I do vaguely remember having to do that in the past. What are you using to do the conversion? Maybe that software is changing the volume levels.

PS: Your thread title mentions "loundness".

Thanks Dave - How do I edit the title.

I'm using Xrecode 3.. I suppose I could try batch encoder although that failed last time I tried. Anybody else got any app recommendations?

[ferneyhoughgeliebte]

Thanks Dave - How do I edit the title.

You don't - you let The Staff do that.

[Dave2002]

Thanks Dave - How do I edit the title.

I'm using Xrecode 3.. I suppose I could try batch encoder although that failed last time I tried. Anybody else got any app recommendations?

I feel sure another member will pop up with some recommendations soon.

As it's something which seems more or less transparent to me, I don't think about this much. It would make sense to get a good work flow, with good tools. I have a feeling that tossing the files into Audacity, or VLC does usually work, though it may also depend on which plug ins are installed.

Have you tried just renaming the files, with a .mp3 extension - I have a vague hunch that works too. As I mentioned, I think our resident mp2 expert will be along soon.

See also https://www.online-convert.com/file-format/mp2

and this https://hydrogenaud.io/index.php/topic,97564.0.html

[johnb]

Dear all,

Thought I would ask here as you seem a knowledge bunch when it comes to Audio related matters. I'm not an Audiophile but do have some nice kit so thought I best start using to best effect (To give you an idea during this process I've learnt that aac is superior to mp3)

So with some Christmas Amazon vouchers I bought myself a Humax FVP 5000 purely for recording radio (I now record SD stuff as well) and chose this model because you can transfer these recordings to your PC's harddrive unencrypted. Essentially what is recorded is an NTS which once transferred is actually an MPEG 2 file (this is how I understand it) I then have to encode this to MP3 to get it to work. This strange thing is , is that a group of files I've been listening to encoded it would seem at 120kbps are much louder than these mp3s at 192kbps.

What gives?

many thanks

I use an older Humax HD-Fox T2 so parts of what I am going to say might not fully apply to your Humax FVP 5000.

For radio, the Humax HD-Fox T2 "records" three files:

filename.hmt
filename.nts
filename.ts

The .ts file contains the actual recording (in .mp2 format), wrapped (together with lots of other stuff) in a "ts" container (or at least a container named as ".ts").
The .hmt file contains general information about the recording (e.g. radio station, text description, dates, etc)
The .nts file is instructed [Edit - s/b *constructed*] by the Humax with timing information, etc to enable the Humax to find its way around the actual recording (which is in the ".ts" file).

The actual audio (contained in the ".ts" file) is in mp2 format and should be (for Radio 3) 192 kbps.

If, in XRecode 3, you set the "Action" to "Extract" it should just extract (or "demux") the mp2 from the .ts file.

If, alternatively, you set the "Output Format" to, say, MP3 it will extract the .mp2 and re-encode it to mp3. As these are both lossy formats this will mean some loss in qualtiy - though whether that loss is audible is another matter.

If you want to edit the resulting mp2 or mp3 file - I suggest using "mp3directcut" which will edit the file without any further degradation. If you use, say, Audacity to edit the file it will decode the mp3/mp2 first and then re-encode the edited data back to mp3/mp2 when you save the file - not ideal for lossy formats.

As far as loudness is concerned - Radio 3 uses a greater dynamic range than probably any other radio station in the UK. This means that the quiet bits are much, much quieter while the very loud bits are (roughly) the same. This means that the average perceived "loudness" will be lower with Radio 3.

[cmr_for3]

I use an older Humax HD-Fox T2 so parts of what I am going to say might not fully apply to your Humax FVP 5000.

For radio, the Humax HD-Fox T2 "records" three files:

filename.hmt
filename.nts
filename.ts

The .ts file contains the actual recording (in .mp2 format), wrapped (together with lots of other stuff) in a "ts" container (or at least a container named as ".ts").
The .hmt file contains general information about the recording (e.g. radio station, text description, dates, etc)
The .nts file is instructed by the Humax with timing information, etc to enable the Humax to find its way around the actual recording (which is in the ".ts" file).

The actual audio (contained in the ".ts" file) is in mp2 format and should be (for Radio 3) 192 kbps.

If, in XRecode 3, you set the "Action" to "Extract" it should just extract (or "demux") the mp2 from the .ts file.

If, alternatively, you set the "Output Format" to, say, MP3 it will extract the .mp2 and re-encode it to mp3. As these are both lossy formats this will mean some loss in qualtiy - though whether that loss is audible is another matter.

If you want to edit the resulting mp2 or mp3 file - I suggest using "mp3directcut" which will edit the file without any further degradation. If you use, say, Audacity to edit the file it will decode the mp3/mp2 first and then re-encode the edited data back to mp3/mp2 when you save the file - not ideal for lossy formats.

As far as loudness is concerned - Radio 3 uses a greater dynamic range than probably any other radio station in the UK. This means that the quiet bits are much, much quieter while the very loud bits are (roughly) the same. This means that the average perceived "loudness" will be lower with Radio 3.

Many Thanks John for such an informative reply.

The loudness bit does make sense and indeed it explains why why I do turn the volume up the sound quality is actually very good. Thanks for the tip on xrecode I had actually played about with extract though it did not solve the volume issue. I shall do that rather than encode as it seems the best way of maintaining quality.

You are also correct about the way in which the Humax records the files but here is the thing. I can only see the three files you describe if I map a drive to the recordings folder and these stay encrypted. If I go through it the "proper" way
browsing via the humax media server in windows explorer then the files show up as mp3 rather than mp2 and changes to the file name with the extension has no effect, programmes still see them as mp3s and won't play them until they've been encoded, and only xrecode seems able to do that. I'll post some screenshots later if that helps (the Media Server seems to have disappeared from windows explorer - another bug bare)

[Beresford]

From a forum about a year ago:
"ts FILES
Actually .ts files are created by DVB-S/DVB-S2 tuners capable of recording transponder streams and can contain mpg2 AC3 AAC h264 mp3, as well as other data ie Teletext or EPG. .ts files contain in most cases just AV data but are not limited to that. VLC can play ts files directly and give you some info about some of the streams in it. Im personally using a sat tuner that records HD channels in .ts files (h264 video and in most cases multiple AAC mp3 mpg2 audio streams). So basically .ts files can contain many different things Its just container format created for sending digital broadcasts over lossy media. VLC can also convert betwen formats (not done this myself)

Using the command line software ffmpeg, I found by experiment that
ffmpeg -ss"00:00:30" -i infilename.ts -acodec copy -t "00:00:20" outfilename.ts

lets me create a new ts file that contains what's in the infile, starting from 30 sec in and lasting 20 sec. The result plays OK on VLC and seems to preserve the data. The ordering of the parts of the command seem critical so the ss has to refer to the input and the -t to the output, etc."

Output file can probably be .wav (for lossless editing) etc, although it might need to be done in a separate step .
Not sure if and where encryption comes in.

[Bryn]

Many Thanks John for such an informative reply.

The loudness bit does make sense and indeed it explains why why I do turn the volume up the sound quality is actually very good. Thanks for the tip on xrecode I had actually played about with extract though it did not solve the volume issue. I shall do that rather than encode as it seems the best way of maintaining quality.

You are also correct about the way in which the Humax records the files but here is the thing. I can only see the three files you describe if I map a drive to the recordings folder and these stay encrypted. If I go through it the "proper" way
browsing via the humax media server in windows explorer then the files show up as mp3 rather than mp2 and changes to the file name with the extension has no effect, programmes still see them as mp3s and won't play them until they've been encoded, and only xrecode seems able to do that. I'll post some screenshots later if that helps (the Media Server seems to have disappeared from windows explorer - another bug bare)

I would simply add a somewhat OT comment re. mp3directcut, i.e., that inaddition to mp3 and mp2, for some versions now it can also edit aac files (the data compression mode used by the iPlayer/Sounds for BBC radio). Don't forget to downloas and include the requisite additional files for mp2/mp2 adn/or aac compatibility.

Many thanks to Martin Pesch for his continuing work on this very useful program.

[johnb]

If I go through it the "proper" way browsing via the humax media server in windows explorer then the files show up as mp3 rather than mp2 and changes to the file name with the extension has no effect, programmes still see them as mp3s and won't play them until they've been encoded, and only xrecode seems able to do that.

I'd be interested to take a look at one of those "mp3" files if you could upload one somewhere.

Alternatively, you could use "MediaInfo" to examine the file and show what it actually contains.

(Perhaps your Humax uses a mp3 filetype when the files aren't actually "normal" mp3 files.)

[johnb]

....
Using the command line software ffmpeg, I found by experiment that
ffmpeg -ss"00:00:30" -i infilename.ts -acodec copy -t "00:00:20" outfilename.ts
....
Not sure if and where encryption comes in.

The Humax automatically encrypts all the files when it writes them to its HDD.

Usually the Standard Definition video and radio files are automatically unencrypted when copied over in certain ways specified by Humax.

If this box operates the same way as the older model I have, the High Definition files are never decrypted and so can't be copied (at least with the official Humax firmware).

In my earlier post I wrote "... in a "ts" container (or at least a container named as ".ts")" because (in the case of my older model) the files it saves to the HDD are actually "m2ts" files but with a ".ts" filetype!

As far as ffmpeg is concerned, the package cmr_for3 is using (Xrecode 3) employs a recompiled version of ffmpeg. One could just use ffmpeg itself as there is a fairly simple command line that will do the job, but for most people the user interface provided by Xrecode 3 will be much more convenient.

One of the reasons that I am sticking with my Humax HD-Fox T2 is that some clever folk wrote terrific customised firmware for it which provides an amazing wealth of facilities which are not otherwise available (including automatic, on HDD, decryption of ALL files, inc. HD, rsync for backup, etc, etc).

[cmr_for3]

Hi John

Thanks for the info, got a mediainfo log file which shows indeed you are correct. I notice we can't upload text files here. Where is an ok place to upload?

[johnb]

cmr_for3, I tend to use Dropbox or Box. There are quite a few other options such as MediaFire, etc, but I have only used Dropbox and Box for some years.

[Dave2002]

One of the reasons that I am sticking with my Humax HD-Fox T2 is that some clever folk wrote terrific customised firmware for it which provides an amazing wealth of facilities which are not otherwise available (including automatic, on HDD, decryption of ALL files, inc. HD, rsync for backup, etc, etc).

Some interesting ideas in that list. Do they apply to the earlyish Humax Freesat boxes? I'd have to check my model number to be sure of which one we've got.

Re mp2 -> mp3 and editing. If by editing one means trimming - cutting, joining, moving audio clips around etc., then there are probably tools which are more or less transparent, and do the operations to produce new files with the audio at exactly the same quality level as the original source (apart from in the regions of the joins, cuts etc.). I used to have a nice mp3 editing tool which worked like that (or so I thought), but it ran on Windows which I've now almost completely abandoned. I'm not sure if my licence would still be valid. However, if the editing requires filtering, volume changes, and other adjustments, then surely all the editing tools will convert the mp2 or mp3 to some other form, then regenerate an appropriately re-encoded output. There will be some slight loss of "quality" in that process, though one has to consider what is meant by "quality". For example, if an audio track has obvious hum - perhaps mains induced, then by using tools such as audacity or other more pro tools, it is feasible to largely remove that noise with a notch filter. The quality "loss" for the rest of the audio will probably be considered insignificant once a suitable improved version with the noise removed is generated.

It does look as though mp2 files should be played by most mp3 players and mp3 software players. How well they do that will depend on implementation - possibly some will be better than others, though I think that most mp2 and mp3 players are nowadays close to optimum - or so I'm led to believe. This wasn't always the case. These lossy formats specify encoding and also are supposed to be quick and easy to decode, and most implementations should be fine nowadays.

[OldTechie]

Encoding of Radio 3 is different for the different delivery methods.

There is a table at https://www.astra2sat.com/radio/uk-d...adio-bitrates/ which seems recent but does have caveats.
I think Freeview and Freesat are both 192kbps MPEG1 LayerII encoding. That is then packaged into an mp2 transport stream. Converting the mp2 stream to mp3 format should be just a matter of repackaging the MPEG1 encoded audio in a different way, but there is a danger that software will choose to decode the original to plain audio and then re-encode it which will further degrade it.

For the Online internet feeds there is information at https://www.bbc.co.uk/sounds/help/ot...odecs_bitrates

It seems from the Astra table that all the iPlayer/Sounds radio is now 320kbps AAC encoded. I was surprised about this, but I checked Radio 2 and the data rate seemed to match:




The rate switches between 43000 and 38000 - so an average of 40000 seems believable. Multiply by 8 because the indication is Bytes not bits and we get 320,000.

Levels may be different. The digital standard in-house uses a reference level of -18dB relative to the digital maximum. The audio is managed to have peaks 8dB above reference, leaving 10dB headroom for mishaps that can be corrected further down the chain. Most of the digital transmissions add the 10dB back to get the maximum volume on the output signal (because,obviously a louder station must be better than a quieter one.) Radio 3 on iPlayer leaves the level alone, so it is likely to be 10dB quieter than other delivery methods. So if there is a peak above the intended levels, you get the correct dynamic range on the iPlayer feed, but all the other will limit the level (and thus compress the audio level.) You'd be hard put to find many occasions where you could hear the degradation this causes.

The iPlayer streams are, I think, delivered using HLS or MPEG-DASH which are good at allowing you to move back in the live stream for catch-up purposes. The lossless audio we had in 2017 was MPEG-DASH.

Personally, I use the one remaining Shoutcast (ICY) stream in the system for Radio 3. This is the same AAC encoding used for Sounds/iPlayer but can be played by foobar2000 by opening the stream from http://open.live.bbc.co.uk/mediasele...adio_three.pls. Foobar2000 can use output methods that bypass the Windows mixer reprocessing of the audio (as can JRiver, but I don't know whether that will work directly from the link.) I have it set to use WASAPI . It means that I play Radio 3 the same way as I play my own library, and I don't accidentally close it by closing a browser window.