Another two stations added to the free to air offerings. There seem to have been significant changes to some of the broadcasters’ bitrates, and indeed several have changed the resolution of their broadcasts.
To gather this data, on 2 through 4 January 2013 I recorded at least six hours, in three separate chunks, from each station onto one of two Topfield PVRs. Then I whacked the minutes and megabytes into a spreadsheet, did the division and subtracted the audio bitrate. These figures probably overstate things a little, depending how much extra the Topfields add into the recording streams (not much, I imagine, because they are standard MPEG files), and the presence of subtitles. So, really, only the first two significant figures of the video bitstream should be considered.
Also, remember, this is in Canberra. The figures may well be quite different elsewhere. Our commercial stations still broadcast their HD as 1,440 x 1,080, for example.
If anyone would like to repeat the process in a major capital city, I’d be happy to email through the spreadsheet on condition that you provide the information back for publication here in due course.
| Station | Ch | Audio format |
Audio bitrate (kbps) |
Video resolution |
Average video bitrate (Mbps) |
|---|---|---|---|---|---|
| ABC1 | 2 | MPEG2 | 256 | 720 x 576i | 4.56 |
| ABC2 / ABC4 | 22 | MPEG2 | 256 | 720 x 576i | 3.98 |
| ABC3 | 23 | MPEG2 | 256 | 720 x 576i | 3.81 |
| ABC News 24 | 24 | DD 2.0 | 256 | 1280 x 720p | 7.94 |
| SBS ONE | 3 | MPEG2 | 192 | 720 x 576i | 3.00 |
| SBS HD | 30 | MPEG2 | 192 | 1280 x 720p | 8.43 |
| SBS TWO | 32 | MPEG2 | 192 | 720 x 576i | 3.03 |
| NITV | 34 | MPEG2 | 192 | 720 x 576i | 3.20 |
| SC10 Canberra | 5 | MPEG2 | 256 | 720 x 576i | 4.85 |
| One Canberra | 50 | DD 2.0 | 448 | 1440 x 1080i | 9.62 |
| TVSN | 54 | MPEG2 | 128 | 544 x 576i | 2.25 |
| ELEVEN | 55 | MPEG2 | 256 | 720 x 576i | 4.18 |
| PRIME7 Canberra | 6 | MPEG2 | 256 | 720 x 576i | 4.64 |
| 7TWO Canberra | 62 | MPEG2 | 256 | 720 x 576i | 4.63 |
| 7mate Canberra | 63 | DD 2.0 | 256 | 1440 x 1080i | 8.54 |
| 4ME | 64 | MPEG2 | 128 | 720 x 576i | 2.21 |
| WIN Canberra | 8 | MPEG2 | 384 | 720 x 576i | 4.55 |
| GEM Canberra | 80 | DD 2.0 | 448 | 1440 x 1080i | 8.22 |
| GOLD | 84 | MPEG2 | 192 | 480 x 576i | 2.45 |
| GO! Canberra | 88 | MPEG2 | 384 | 720 x 576i | 4.09 |
Things to note:
- ABC used to broadcast on ABC3 at a reduced 2Mpbs bitrate during the hours that it is closed overnight. Now it maintains the same bitrate overnight (the picture during these times is largely static panels with a little light animation on them). However from program to program there is a fair amount of flexibility in the bitrate
, suggesting ABC still re-allocates the bandwidth available according to the balance of programming. It’s just that they allow too much for that near-static overnight stuff on ABC3.
- SBS has made two big changes: it has added the NITV (National Indigenous TV) channel, and changed the resolution of its HD channel from 720p50 to 1080i50. The former has sucked quite a bit of bandwidth from the existing stations, reducing SBS One from 4.5Mbps last time to just 3Mbps.
- Southern Cross Ten has added an advertising channel, TVSN, with a low audio bitrate and low resolution (544 rather than 720 pixels wide). A little of this channel’s resources has been drawn from SC10, the main channel, but most has come from the HD ONE Canberra, which has fallen from 11.46 to 9.62Mbps
- Prime has reduced the average bitrate of its advertising channel, 4ME, yet at the same time bumped its resolution back to the original 720 x 576 from 544 x 576. It has retained the same lower audio bitrate, though, of 128kbps.
- WIN’s GOLD channel has had its bitrate bumped up from an appalling 1.5Mbps to 2.45Mbps, although the resolution has remained the same at 480 x 576, a full third below the norm. It also has a too high audio bitrate of 192kbps. Indeed, WIN continues to waste lots of bits on audio for all its stations: 384kbps for the two SD ones and 448kbps for its HD station. Bringing the SD ones down to 192kbps would bring them into line with the bulk of 2.0 audio on DVD, and given that the HD is rarely if ever in 5.1 mode, 448kbps is a bit over the top. Changing to 192kbps all around, except for 128kbps for GOLD, would release about 0.7Mbps which could be spent on improving picture quality.
- ONE Canberra remains the winner for HD bitrate, by a greatly reduced margin, at 9.62Mbps (the others are around 8.5Mpbs).
- The winner for SD bitrate is SC10 Canberra on 4.85Mbps, down from 5.14Mbps.
5 Responses to Digital TV video bitrates – January 2013