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Blu-Ray and HD-DVD are high-density optical discs with storage capacities ranging from 15GB to 50GB, designed to support the MPEG-2 compression used in DTV standards as well as new codecs such as H.264 and VC-1, which are mandatory for all players. Blu-Ray and HD-DVD distributed by studios for motion picture reproduction use data rates of 28-40 Mbps for video content ensuring at least 3 Hrs of full HD resolution content playable on a dual-layer 50GB disc. The range of bitrates suistainable is however much wider and Blu-Ray and HD-DVDs can be recorded at lower bitrates to ensure an extended recording time.
PVRs records video in digital format onto a hard disk drive. The term PVR includes stand-alone boxes with record functionality, set-to-boxes with added storage and dedicated software programs running on PCs. The capacity of a PVR varies greatly, from 80GB in cheaper STB models to 160/250GB easily found in most PCs today. PVRs tend to offer support for DTV MPEG-2 formats as well as H.264, although VC-1, VP6 and other codecs are encountered, especially in PC based PVRs.
Extended play
As an example application, when coupled with an HDTV tuner/demodulator, the Blu-Ray/HD-DVD recorder could be used to save the MPEG-2 20Mbps transport stream to disc. This would ensure more than 5hrs playback on a dual-layer Blu-Ray disc and about 4 hrs on an HD-DVD. In a system utilising Q, however, the values can be more than doubled by transcoding the content to a more efficient H.264 stream at 8-10 Mbps and bringing the recording time up to over 14 hrs on a dual-layer Blu-Ray disc. Resizing to SD resolutions would bring the total recordable time to over 50 hrs. The same principle applies to PVRs where the space restriction is that of the hard-drive rather than the optical disc.
The table below highlights the space-saving advantages derived from transcoding and/or transrating. |
| Recordable time (hrs:mins) |
| signal |
codec |
indicative bitrate [Mbps] |
Blu-Ray |
HD-DVD |
DVD |
80GB PVR |
| |
50 GB |
30 GB |
8.5 GB |
80 GB |
| Broadcast HDTV |
MPEG-2 |
20.0 |
5:41 |
3:24 |
|
9:06 |
| |
H.264 |
10.0 |
11:22 |
6:49 |
|
18:12 |
| |
H.264 (LP) |
5.0 |
22:45 |
13:39 |
|
36:24 |
| HD movie |
MPEG-2 |
29.4 |
3:52 |
2:19 |
|
6:11 |
| |
H.264 |
15.5 |
7:20 |
4:24 |
|
11:44 |
| |
H.264 (LP) |
7.8 |
14:35 |
8:45 |
|
23:20 |
Broadcast SD (PAL) |
MPEG-2 |
8.0 |
14:32 |
8:32 |
2:25 |
22:45 |
| |
H.264 |
4.0 |
28:26 |
17:04 |
4:50 |
45:30 |
| |
H.264 (LP) |
2.0 |
56:53 |
34:08 |
9:40 |
91:01 |
|
Multiple sources
Other applications can include direct recording directly to Blu-Ray / HD-DVD from HD camcorders, either from an AVCHD output (H.264 stream at ~20Mbps) or an uncompressed HDMI output where available. Other sources may include HD webcams, security cameras, laptops and PCs, etc.
Increased device functionality
When Q is integrated within the HD recorder it may be exploited to further transform the content, beyond the recording parameters of Blu-Ray / HD-DVD to the requirements of any external device connected to the recorder through an external USB port, for example. The table below highlights the need for transcoding/transrating.
| Device |
MPEG-2 |
H.264 |
VC-1 |
Max Resolution |
Max bitrate |
| Blu-Ray movie |
yes |
yes |
yes |
1920x1080 |
40 Mbps |
| HD-DVD movie |
yes |
yes |
yes |
1920x1080 |
29.4
Mbps |
| iPod |
|
yes |
|
320x240 |
768 Kbps |
| Zune |
|
yes |
yes |
320x240 |
736 Kbps |
| PSP |
|
yes |
|
480x272 |
1.5 Mbps |
| Laptop |
yes |
yes |
yes |
1920x1080 |
50-100 Mbps |
| * capabilities for these devices
are indicative and depend on both hardware and
firmware |
Security
Q includes HDCP with secrue keystore, a built-in AES/3DES encryption block and software programmable DRM algorithms to ensure that premium and protected content is transcoded securely and the necessary DRM is applied to it before being burned to disc, saved to a hard-drive and/or stored on an external device. |
