Sunday, April 27, 2014

The State of MPEG-DASH Deployment

People have been recently discussing some of the points raised by this article at Streaming Media Website, it’s worth a read. A few of the points from the article worth noting;

LTE Broadcast and Pay TV.
  • With LTE Broadcast the device can switch on the fly from a unicast DASH session to a multicast DASH session. 
  • This broadcast/multicast DASH session only has one variant stream. 
  • On congested cells it provides a mechanism to deliver content to more users. 
  • Could CC leverage this ability in some way?

  • Netflix a bit like YouTube don’t use the DASH standardised MPD (Media Presentation Description) to detail all available variants, which means they aren’t really DASH, in my opinion. They use one the file formats specified in Dash, a variant of MP4 file format. This is a trend we have seen content providers follow, choosing parts of the standard they like and not others. 
  • Netflix and YouTube are using CENC (Common Encryption) standard as supported by DASH to DRM their content. This provides the ability to switch to different DRM providers and not to be tied to one specific version. 
  • HbbTV (Hybrid Broadcast Broadband TV) TV sets are reported to becoming available to consumers. The latest version of the HbbTV specification supports DASH only formatted content for DRM protected content.
Further Reading
Multicast-broadcast single-frequency network http://en.wikipedia.org/wiki/Multicast-broadcast_single-frequency_network




Ericsson LTE Broadcast http://www.ericsson.com/ourportfolio/telecom-operators/lte-broadcast

CENC http://docs.unified-streaming.com/documentation/protect/common-encryption.html

HbbTV https://www.hbbtv.org/


Thursday, April 24, 2014

H.265 Presets

x265 has a number of predefined --preset options that make trade-offs between encode speed (encoded frames per second) and compression efficiency (quality per bit in the bitstream). The default preset is medium, it does a reasonably good job of finding the best possible quality without spending enormous CPU cycles looking for the absolute most efficient way to achieve that quality. As you go higher than medium, the encoder takes shortcuts to improve performance at the expense of quality and compression efficiency. As you go lower than medium, the encoder tries harder and harder to achieve the best quailty per bit compression ratio.


The presets adjust encoder parameters to affect these trade-offs.

ultrafastsuperfastveryfastfasterfastmediumslowslowerveryslowplacebo
ctu32323264646464646464
bframes4444444888
b-adapt0000222222
rc-lookahead10101515152025304060
scenecut0404040404040404040
refs1111333355
mediahexhexhexhexhexstarstarstarstar
merange25445757575757575792
subme0112223345
rect0000001111
amp0000000111
max-merge2222223345
early-skip1111000000
fast-intra1111100000
fast-cbf1111000000
sao0111111111
signhide0111111111
weightp0011111111
aq-mode0022222222
cuTree0000111111
rdLevel2222234666
lft0111111111
tu-intra1111111234
tu-inter1111111234

Placebo mode further enables transform-skip prediction analysis (lossless).
–tuneeffect
psnrdisables adaptive quant, psy-rd, and cutree
ssimenables adaptive quant auto-mode, disables psy-rd
fastdecodeno loop filters, no weighted pred, no intra in B
zerolatencyno lookahead, no B frames, no cutree