[Ffmpeg-devel] [ bug ] converting png to dv gives solid black

Måns Rullgård mru
Mon Mar 13 16:07:21 CET 2006

Erik Slagter said:
> On Mon, 2006-03-13 at 13:32 +0000, M?ns Rullg?rd wrote:
>> >  - NTSC has nothing to do with frame rates
>> NTSC is the very committee that specified those frame rates.  The acronym
>> has subsequently been overloaded with a number of meanings.  Sometimes it
>> is used to refer to frame sizes, sometimes frame rates, and sometimes chroma
>> encodings.  In a sense they are all correct.  All these parameters were
>> part of the system defined by NTSC some 50 years ago.
> Still "NTSC" is not a frame rate. There are regions that watch NTSC
> modulated colour using 25 frames per second. I don't know from the top
> of my head where, but I can dig if necessary. NTSC B or NTSC G or
> similar.

The NTSC system comes in several variants, true.

>> Analog or digital, SD or HD, you still have to use *some* frame rate.  The
>> proper choice depends on the specific context.  The problems only arise when
>> you need to convert content to another frame rate.  If codecs, containers
>> and displays all support arbitrary frame rates the problem will go away.
> Okay, from a technical perspective it doesn't matter that much, I agree,
> the computer won't mind using a crystal (eg) 0.001% different to
> compensate for a "weird" frame rate. But personally I prefer having to
> write 30 fps to 30000/1001, don't you?

Sure.  The fact remains that there is lots of content recorded at a native
30000/1001 fps frame rate.

>> Interlacing is pure evil, though.
> :-) It's a bit like marketing, it promises all sorts of things it
> actually never completely meets.
>> > I really hope this silly technical artifact dies very soon, as will NTSC
>> > (and PAL and SECAM).
>> I'm afraid that won't happen all that soon.
> I was talking of the colour modulation techniques, which they refer to.
> Analogue TV gone -> colour modulation gone.

Not quite true.  The digital settop boxes will continue to output analog
composite or svideo signals for quite some time to come.

> Over here (NL) at last digital TV is taking off, using DVB-S (been
> available for ages) DVB-T (available for a few years) and DVB-C
> (available since recently). Especially the last one seems promising, in
> marketing terms, many people are considering it, and the cable companies
> push it, because it's more profitable for them. DVB-T cannot be expanded
> any further because the necessary frequencies are in use for analogue TV
> distribution, so there is some pressure to stop broadcasting analogue TV
> completely and re-use the frequencies for DVB-T. Although I am not too
> enthusiastic about DVB-T (merely because of the horrible bitrate used
> here) at least it's better than analogue.

Sounds about like the situation here in the UK.  DVB-T isn't great, but at
least where I live, it is better than the analog signal.  It's widescreen
too, which is always good.

M?ns Rullg?rd
mru at inprovide.com

More information about the ffmpeg-devel mailing list