[theora] Http adaptive streaming for html5

Richard Watts rrw at kynesim.co.uk
Mon Jan 4 10:02:36 PST 2010

Eric Carlson wrote:
> On Dec 28, 2009, at 9:50 AM, Richard Watts wrote:

[ I shall get back on this soon, promise! Figured I should read the
HTML5 spec before I waded in again and it's taking a while - thus
far, I basically reckon Silvia's absolutely right .. however,
just quickly .. ]

>>  My first objection is the $2.50/unit I need to pay to the MPEG-LA
>> for the MPEG 2 Systems licence to package my video as TS/PS.
>   This is a question for the lawyers, and I am *definitely not* a lawyer, but as far as 
> I know no licensing fee is required to create a transport stream.


  There's actually a handy list of claims somewhere near there. The
MPEG-LA don't generally bother with pure software encoders (or in
fact pure software decoders - VLC and ffmpeg have been happily violating
MPEG-LA's patents for years without much trouble), but they
do care fairly passionately about embedded devices, decoders and STBs
that use PS or TS. It's not vitally vitally important, but sooner
or later you will get a big scary letter telling you to pay up.

  In fact, it's perfectly likely that attempts to avoid the MPEG-2
systems patent portfolio are pointless and you'd technically have to
pay them anyway, but let's at least try not to be patent encumbered
when we can avoid it :-).

  Obviously, this doesn't make any difference if all you care about
is non-embedded free software, but it's a right pain if you're trying
to manufacture devices that play open formats only to discover that you
get killed on the royalties for doing so, particularly when it's

>>  My second is that many hardware demuxes find it extremely
>> difficult to cope with PATs and PMTs following each other directly
>> and with them immediately preceeding an Iframe. It's going to make
>> life hard for STBs and anyone else who doesn't have the computing
>> power to do everything software. In practice, you will get a
>> frame skip every time you go over a file transition.
>   I don't know anything about this issue, but a streaming engineer here tells me 
> "[I have never seen a stream] that didn't have pat and pmt together".

  Running tsinfo (from tstools.berlios.de) on the first UK DVB mux
I could find:

Packet 1246 is PAT
Program list:
     Program 4173 -> PID 104d (4173)
     Program 4351 -> PID 10ff (4351)
     Program 4415 -> PID 113f (4415)
     Program 4479 -> PID 117f (4479)
     Program 4671 -> PID 123f (4671)
     Program 4237 -> PID 108d (4237)
Multiple programs in PAT - using the first

Packet 2693 is PMT with PID 104d (4173)
   Program 4173, version 6, PCR PID 0258 (600)
   Program streams:
     PID 0258 ( 600) -> Stream type 02 (  2) H.262/13818-2 video 
(MPEG-2) or 11172-2 constrained video


>>  My third is that it introduces yet another file format to a program
>> that really doesn't need one (and it's not visible to JS either).
>> What's wrong with XML?
>   The file format is *extremely* simple, why use XML for something 
>   like this that doesn't require the complexity? 

  Because XML is there already and doesn't require yet another
spec for how you manipulate it in the DOM.


More information about the theora mailing list