BackEnd

Keybinding Markup

---
title: BackEnd
---

Implemented by
:   [Hastur][1], [Cyclops][2]

## Back end

*   Record and playback on DVB-T 
*   DVB-T (Freeview) 
*   Simultaneous record and playback 
*   Media sharing

* * *

# Hardware

## Back-end

*   Dual TV and DVB-T tuner card(s) 
*   [Storage Server][3] connection

* * *

# Operating Systems

*   [Debian][4] 
*   [OpenSolaris][5] 
*   [Nexenta][6] - Ubuntu/Solaris

* * *

# Data Partitioning

*   Separate metadata and library trees allows some clients to collect metadata

## Single Volume

*   Each MEDIATYPE has separate library and metadata trees 
*   Data trees are grouped for export using "bind" mounts 
*   Matches nfs export concept

## Logical Volumes Option

*   Each MEDIATYPE has a logical volume, lv-MEDIATYPE 
*   Each lv-MEDIATYPE has separate library and metadata trees 
*   Trees are grouped for export using normal mounts 
*   Requires a resizeable filesystem (i.e. not XFS)

# File Permissions

*   Requires ACLs

## Users

| media-centre | Default owner | rw all media |
||

## Groups

| Group        | Role               | Permissions      |
|:------------ | ------------------ | ---------------- |
| mc-music     | Plays music        | ro music lib     |
| mc-videos    | Plays videos       | ro video lib     |
| mc-movies    | Plays movies       | ro movies lib    |
| mc-photos    | Shows photos       | ro photos lib    |
| mc-tv        | Plays recordings   | ro recordings    |
| mc-games     | Plays games        | ro game roms lib |
| mcadm-music  | Manages music      | rw music library |
| mcadm-videos | Manages videos     | rw video library |
| mcadm-movies | Manages movies     | rw movie library |
| mcadm-photos | Manages photos     | rw photo library |
| mcadm-tv     | Manages recordings | rw recordings    |
| mcadm-games  | Manages games      | rw game roms lib |

*   All media files have owner permissions "rwx" 
*   All media files have group (ACL mask) permissions "rwx" 
*   All media files have other permissions "\---|" 
*   All MEDIATYPE files have named group "mcadm-MEDIATYPE" permissions "rw-" 
*   All MEDIATYPE files have named group "mc-MEDIATYPE" permissions "r--" 
*   All MEDIATYPE directories have default ACLs reflecting the above permissions

## Example Configuration

`/etc/passwd`

media-centre:x:3000:3000:Media Centre:/nonexistent:/usr/sbin/nologin

Example `/etc/group`

mc-movies:x:3003:mythtv,mediatomb,admin1,user1
    mc-music:x:3001:mythtv,mediatomb,mpd,admin1,user1
    mc-photos:x:3007:mythtv,admin1,user1
    mc-tv:x:3009:mythtv,mediatomb,admin1,user1
    mc-videos:x:3002:mediatomb,admin1,user1
    mcadm-movies:x:3006:,admin1
    mcadm-music:x:3004:mpd,admin1
    mcadm-photos:x:3008:,admin1
    mcadm-tv:x:3010:,admin1
    mcadm-videos:x:3005:,admin1
    mc-users:x:3011:admin1,user1

Example ACL (`getfacl /mnt/media/movies`)

# file: library
    # owner: media-centre
    # group: mcadm-movies
    user::rwx
    group::---
    group:mc-movies:r-x
    group:mcadm-movies:rwx
    mask::rwx
    other::---
    default:user::rwx
    default:group::r-x
    default:group:mc-movies:r-x
    default:group:mcadm-movies:rwx
    default:mask::rwx
    default:other::---

# User Contributed Files

*   All users have a `$user/shared-media` directory with write permission 
*   `$user/shared-media` ACLs allow access by mediasys groups 
*   `mediasys/users/$user` is a symlink to `$user/shared-media` 
*   CIFS requires `wide links = yes` for the `mediasys` share. 
*   Not compatible with NFS.

# Data Export

*   A single shared tree for mediasys 
*   Each MEDIATYPE library and metadata directory is mapped into the single tree. 
*   Shares per MEDIATYPE writeable by the admin group for that MEDIATYPE.

## Example fstab

`/etc/fstab`

# Media mounts
    /dev/vg-media/home        /home   ext4    defaults,noatime,nosuid,noauto,acl      0       0
    /dev/vg-media/media       /mnt/media  ext4    defaults,noatime,nosuid,noauto,acl      0       0
    # Export mounts
    /mnt/media/movies/library /export/mediasys/movies/library none bind,noauto    0       0
    /mnt/media/movies/metadata /export/mediasys/movies/meta none bind,noauto      0       0
    /mnt/media/music/library /export/mediasys/music/library none bind,noauto      0       0
    /mnt/media/music/metadata /export/mediasys/music/meta none bind,noauto        0       0
    /mnt/media/tvshows/library /export/mediasys/tvshows/library none bind,noauto  0       0
    /mnt/media/tvshows/metadata /export/mediasys/tvshows/meta none bind,noauto    0       0
    /mnt/media/recordings /export/mediasys/recordings none bind,noauto    0       0
    /mnt/media/photos/library /export/mediasys/photos/library none bind,noauto    0       0
    /mnt/media/photos/metadata /export/mediasys/photos/meta none bind,noauto      0       0

## Samba/CIFS

*   Requires username/password

### Example Configuration

`/etc/smb.conf`

[mediasys]
       path=/export/mediasys
       browseable = yes
       writable = yes
       mangled names = no
       follow symlinks = yes # for per-user shared-media
       wide links = yes  # for per-user shared-media
       valid users = mythtv,@mc-users
    
    [homes]
       path=/home/%S
       comment = Home Directories
       browseable = no
       writable = yes
       create mask = 0700
       directory mask = 0700
       valid users = %S
       mangled names = no
    
    # Administrative shares - not browseable by default
    [movies]
       path=/mnt/media/movies
       browseable = no
       writable = yes
       mangled names = no
       valid users = @mcadm-movies
    
    ...

## NFS

Read-only Exports (without security)

`/etc/exports`

/export/mediasys  192.168.0.0/24(ro,fsid=0,sync,no_subtree_check)
    /export/mediasys/movies/library   192.168.0.0/24(ro,nohide,sync,no_subtree_check)
    /export/mediasys/movies/meta      192.168.0.0/24(ro,nohide,sync,no_subtree_check)
    /export/mediasys/tvshows/library  192.168.0.0/24(ro,nohide,sync,no_subtree_check)
    /export/mediasys/tvshows/meta     192.168.0.0/24(ro,nohide,sync,no_subtree_check)
    /export/mediasys/music/library    192.168.0.0/24(ro,nohide,sync,no_subtree_check)
    /export/mediasys/music/meta       192.168.0.0/24(ro,nohide,sync,no_subtree_check)
    /export/mediasys/photos/library   192.168.0.0/24(ro,nohide,sync,no_subtree_check)
    /export/mediasys/photos/meta      192.168.0.0/24(ro,nohide,sync,no_subtree_check)

Permissions fixes for NFSv3

/export/mediasys 192.168.0.0/24(ro,fsid=0,sync,no_subtree_check,all_squash,anongid=3000)
    /export/mediasys/movies/library 192.168.0.0/24(ro,nohide,sync,no_subtree_check,anongid=3003)
    ...

mount -t nfs4 -o ro media: /mnt/media

[[$[Get Code]]][9]

* * *

# Capture Cards

## Linux Chipset Support

[ivtv Driver supported hardware][10]

*   CX23415 
*   CX23416

## DVB-T

*   [http://www.linuxtv.org/wiki/index.php/DVB-T\_PCI\_Cards][13] 
*   [http://www.linuxtv.org/wiki/index.php/DVB-T\_PCIe\_Cards][14]

| **Card**                                   | HD  | **SD tuners** | **DVB-T tuners** | **Price**             | **Notes**                              |
||
| Nova-T-PCI                                 | Yes |               | 1                | £28 [Ebuyer][15]      | Supported                              |
| Nova-T-500                                 | Yes |               | 2                | £55 [Ebuyer][16]      | USB bridge device; not fully supported |
| Pinnacle PCTV DVB-T Pro PCI                | No  |               | 2                | £56 [scan][17]        | No support                             |
| [DViCO FusionHDTV Dual Digital][18]        | Yes |               | 2                |                       |                                        |
| AverTV DVB-T A771             |     |               |                  | £35 [SpecialTech][20] |                                        |
| AverTV DVB-T A777             | Yes |               | 1                | Supplier??            | Replaces A771                          |
| TerraTec Cinergy 2400i PCI-E  |     |               | 2                |                       | [No support yet][22]                   |
| Compro VideoMate DVB-T200 PCI | Yes |               | 1                |                       |                                        |

* * *

# CAMs

*   <http://www.divineo.co.uk/cgi-bin/div-uk/elv-phoenix.html> (can use for Nova-T PCI)

* * *

# DVD Encoding

*   <http://lipas.uwasa.fi/~f76998/video/conversion/> 
*   [Test Videos][25]

## Profiles

### High Quality Compressed

*   H.264 video 
*   AC3 audio 
*   mp4 container 
*   ~2GB

### High Quality Raw

*   MPEG2 
*   AC3 audio 
*   VOB 
*   ~9GB

* * *

# Notes

*   Hardware or software encoding? 
    *   Hard enc more expensive, Soft enc needs more powerful CPU 
        *   No encoder needed, DVB-T is MPEG2. MPEG2->MPEG4 needed anyway 
*   Does a software encoder require encoding to MPEG2? 
    *   Yes, or some other codec 
*   Can a software encoder encode to something else in Realtime? 
    *   DivX, Xvid, H.264 check processor requirements 
*   MPEG-4 encoders 
    *   Hauppauge HVR-4000 does H.264 
*   Front end may need up to 1GB RAM to store MythTV UI elements for 1080p displays 
*   VIA UniChromePro graphics may eventually be capable of H.264 acceleration with XvMC 
*   VIA & nVidia cards can accelerate decoding of MPEG2

[1]: /Network/Hastur
 [2]: /Network/Cyclops
 [3]: /Network/StorageServer
 [4]: http://www.debian.org/
 [5]: http://opensolaris.org/
 [6]: http://www.nexenta.org/
 [9]: BackEnd?action=sourceblock&num=1
 [10]: http://ivtvdriver.org/index.php/Supported_hardware
 [13]: http://www.linuxtv.org/wiki/index.php/DVB-T_PCI_Cards
 [14]: http://www.linuxtv.org/wiki/index.php/DVB-T_PCIe_Cards
 [15]: http://www.ebuyer.com/UK/product/27669
 [16]: http://www.ebuyer.com/customer/products/index.html?product_uid=113946
 [17]: http://www.scan.co.uk/Products/ProductInfo.asp?WebProductID=483571
 [18]: http://www.fusionhdtv.co.kr/ENG/Products/DualDigital.aspx
 [20]: http://www.specialtech.co.uk/spshop/customer/product.php?productid=535
 [22]: http://www.linuxtv.org/wiki/index.php/TerraTec_Cinergy_2400i_DVB-T
 [25]: http://www.digital-digest.com/dvd/downloads/trailers.html

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