Comments on: HD video podcasts come to iTunes--and Apple TV

The 'Washington Post' has launched the first HD video podcast available on iTunes and Apple TV.

[drhamad]

Bitrate comparisons to DVD are irrelevant... maybe

I've never quite figured out how iTMS manages to have such large files for such low quality... and even here, with 3rd party encoded content, the same thing happens. Why on earth would the bitrates need to be so high? When I encode video in h.264, I use between a 1,300 and 1,500 kbps video bitrate and 320kbps AAC audio. This results, when using h.264 and NOT MPEG-4, in full movies at between 1 and 1.5 GB, and the quality is superb (based on a DVD). So what is iTunes (especially, since it theoretically uses 480p) and the Washington Post (less so) doing wrong? What the heck are they using?

[Daniel L Smith]

Bit rate doesn't measure absolute quality

"The problem here isn't resolution but bitrate--4,061 kbps with a mono
soundtrack. That's a big improvement over the 1,516 kbps encoding found
on a purchased episode of The Office, but merely 40 percent of the 10
megabit capacity found on a standard-definition DVD."

Serious problems with this statement:

- Resolution directly affects bit rate. The difference between 480p and 720p
is 1.5^2 = 2.25, meaning an HD video with the *same* quality would be 2.25
times larger (3,411). So the "big improvement" is only 4061/3411 = 19%.

- You can't infer quality by comparing bit rates of different codecs (MPEG-2
on DVDs vs. H.264 on iTunes) any more than you can compare bit rates of
audio files (mp3 vs. aac) or clock speeds of processors (Intel vs. PowerPC). H.
264 is supposed to use far superior compression, when compared with its
predecessors. It had better *not* require nearly the bit rate of a DVD to
produce good-quality results, or something is seriously wrong.

[juzzle]

Washington Post HD? - cropped windows

Perhaps I skipped over the coverage of this article, however, whilst the supposed HD content by The Washington Post was better that TV Shows from iTunes, it was cropped to about 75% of the screen area. I am not talking about 4:3 bars, I am talking about the 16:9 reduced to take up less pixels. I suspect what they've produced is about 580px high, and not the full 720p. A bit of a stretch (shrink?) if you ask me :-/