Which recordings take the most space?

[Last.To.Know]

If you are referring to the two Fred Astaire - Ginger Rogers films, I have not yet played them.

I did watch Porridge, which I'm fairly certain was 4:3, and as we can see, took up more GB/min than the film Jimi: All Is by My Side on the same channel.

 

[Luke]

For my own amusement/satisfaction, I pasted the values from the Web-If Media Details box for various recordings into Excel.

Quite surprised to see the variation between similar recordings on the same channel broadcast at the same time of day.

Title	Length (Minutes)	FileSize (GB)	GB/Min.	Channel	Type
Mister John	90​	2.24​	0.02489​	BBC ONE HD	Film
Jimi: All Is by My Side	109​	2.84​	0.02606​	BBC TWO HD	Film
Agatha Christie's Crooked House	121​	3.33​	0.02752​	Channel 5 HD	TV
Carefree	84​	2.55​	0.03036​	BBC TWO HD	Film
Porridge	45​	1.41​	0.03133​	BBC TWO HD	TV
Beat The Chasers	60​	2.15​	0.03583​	ITV HD	TV
Joe Lycett	56​	2.12​	0.03786​	Channel 4 HD	TV
Tropic Thunder	98​	4.22​	0.04306​	BBC ONE HD	Film
The Gay Divorce	101​	4.75​	0.04703​	BBC TWO HD	Film
The Conversation	109​	5.22​	0.04789​	BBC TWO HD	Film

These two Fred Astaire - Ginger Rogers films, Carefree and The Gay Divorce, are poles apart.

Looking at that selection you could interpret it that, in total, the third item has taken up far more room than "The Gay Divorce". You have only had a recording of the "The Gay Divorce" for under a month, but the third item you have had for 6 months.

 

[af123]

Size can also vary depending on how big the EPG data was at the time of broadcast, since it is interspersed with the programme data. Stripping the recordings will remove that possible noise and be informative.

 

[Last.To.Know]

Size can also vary depending on how big the EPG data was at the time of broadcast, since it is interspersed with the data. Stripping the recordings will remove that possible noise and be informative.

I understand all these words individually, but not necessarily in this order...

You're saying that EPG data is embedded in each recording's file?

What would be the process to strip this data out?

 

[Luke]

What would be the process to strip this data out?

Via the Shrink function of the web-if. Space savings are about 4% for HD, 20% for SD and at least 75% for radio.

 

[EEPhil]

You're saying that EPG data is embedded in each recording's file?

Yes.

 

[Black Hole]

You're saying that EPG data is embedded in each recording's file?

What would be the process to strip this data out?

You don't have to live up to your moniker you know

 

[Last.To.Know]

Size can also vary depending on how big the EPG data was at the time of broadcast, since it is interspersed with the data. Stripping the recordings will remove that possible noise and be informative.

You don't have to live up to your moniker you know

Why Not?

It gets me the answers I need.

And to remove all doubt, my follow-up question is...

When people say the file contains the EPG data,
are they referring to the entire 8 days worth of all channels
(which seems preposterous even to me)?

Or just the data about the specific programme, which I would be surprised if that took up so much space?

 

[Black Hole]

are they referring to the entire 8 days worth of all channels

Yes. And other stuff.

The data on a mux is like lots of streams within a container file. If a media file has (say) alternative points-of-view, or alternative language channels, the users pick what streams they want for presentation at the point of presentation. Ditto the data stream in a DVB mux - there are streams for each service, and streams of general information. A recording comprises the streams for one service plus the general information. Shrink ditches the general information, so after that all the metadata has to come from whatever is captured in the .hmt file.

Bear in mind the general information is a fairly small proportion of the data in a recording, so it could have been considered a better option to keep it than to ditch it, or maybe the terms of the Freeview+ licence insist recorder manufacturers keep it in.

 

[af123]

When people say the file contains the EPG data,
are they referring to the entire 8 days worth of all channels
(which seems preposterous even to me)?

Oh yes, all of that is broadcast on every mux, over and over again, interlaced with the programme data, and ends up in the recording files.

Bear in mind the general information is a fairly small proportion of the data in a recording,

That really depends, that's why I would strip it out before performing comparisons between channels and programmes.

Here's a fine example from Pick...


That's almost 300MiB of EPG data in a 30 minute recording. I don't know if this rate is fairly consistent across each mux or whether the bit rate is reduced statistically along with the other data.

 

[MymsMan]

When people say the file contains the EPG data,
are they referring to the entire 8 days worth of all channels
(which seems preposterous even to me)?

Yes and not just once but continuously repeated.
If you think about it how else would a basic set top box with no internet connection be able to display a full eight day epg within a few seconds of being switched on.
Possibly it could have been stripped out in the recording process, but for whatever reason it isn't, so it forms part of every recording that hasn't been shrunk.

The target market was as a HD TV recorder not as a Radio recorder so even if Humax had expended the effort to build in shrinking it would not have made that much difference to the advertised capacity of the machine (in recording hours)

If you use detectads with cropping that automatically includes decryption and shrinking but otherwise shrinking is probably not worth it for programmes that you are going to watch once and then delete but for programmes that you intend to keep for a while it can be worth decrypting and shrinking so that they are smaller and more portable.

 

[EEPhil]

The target market was as a HD TV recorder not as a Radio recorder

With so much dross on TV these days, my Humax is more of a radio recorder.
In a way I'm glad Humax don't remove the epg info in the recordings. Some of their boxes (5000T) don't have a .hmt file with epg info for the programme. The fact that this information is in the .ts file means the "sidecar" utility (Windows version) is very useful - for me.

 

[Last.To.Know]

Well, thank you all for your replies on this EPG data subject, which is a complete revelation to me.

It explains why the updated table looks like this.

Title	Length	FileSize	GB/Min.	Channel	Type
Mister John	90​	2.24	0.02489	BBC ONE HD	Film
Jimi: All Is by My Side	109​	2.84	0.02606	BBC TWO HD	Film
Agatha Christie's Crooked House	121​	3.33	0.02752	Channel 5 HD	TV
Carefree	84​	2.55	0.03036	BBC TWO HD	Film
Porridge	45​	1.41	0.03133	BBC TWO HD	TV
Beat The Chasers	60​	2.15	0.03583	ITV HD	TV
Joe Lycett	56​	2.12	0.03786	Channel 4 HD	TV
Tropic Thunder	98​	4.22	0.04306	BBC ONE HD	Film
The Gay Divorce	101​	4.75	0.04703	BBC TWO HD	Film
The Conversation	109​	5.22	0.04789	BBC TWO HD	Film
A Knight's Tale Pt.1	59​	3.7	0.06271	Channel 5 HD	Film
A Knight's Tale Pt.2	99​	4.61	0.04657	Channel 5 HD	Film

And why the first part of A Knight's Tale has a GB/min rate which is a third higher than the second part.

 

[grahamlthompson]

Well, thank you all for your replies on this EPG data subject, which is a complete revelation to me.

It explains why the updated table looks like this.

Title	Length	FileSize	GB/Min.	Channel	Type
Mister John	90​	2.24	0.02489	BBC ONE HD	Film
Jimi: All Is by My Side	109​	2.84	0.02606	BBC TWO HD	Film
Agatha Christie's Crooked House	121​	3.33	0.02752	Channel 5 HD	TV
Carefree	84​	2.55	0.03036	BBC TWO HD	Film
Porridge	45​	1.41	0.03133	BBC TWO HD	TV
Beat The Chasers	60​	2.15	0.03583	ITV HD	TV
Joe Lycett	56​	2.12	0.03786	Channel 4 HD	TV
Tropic Thunder	98​	4.22	0.04306	BBC ONE HD	Film
The Gay Divorce	101​	4.75	0.04703	BBC TWO HD	Film
The Conversation	109​	5.22	0.04789	BBC TWO HD	Film
A Knight's Tale Pt.1	59​	3.7	0.06271	Channel 5 HD	Film
A Knight's Tale Pt.2	99​	4.61	0.04657	Channel 5 HD	Film

And why the first part of A Knight's Tale has a GB/min rate which is a third higher than the second part.

Vbr increases the bitrate when there is a lot of rapid movement. Statmuxing will pinch bandwidth from channels on the same mux with less demanding content. To see this you would need to look at the other channels on the same mux. Basically every mux has a maximum bitrate. This is shared according to the programme content. Football for instance will be demanding on bitrate.