[PLUG] MythTV Testing - HDTV choppy

King Beowulf kingbeowulf at gmail.com
Sat Sep 21 00:11:45 PDT 2013


On 09/20/2013 04:44 PM, Dick Steffens wrote:
> I'm testing Mythbuntu on an Toshiba Satellite laptop. Everything 
> installs and runs. I have a simple dipole antenna connected to an 
> HDHomeRun box connected to my home network. I can see a number of
> local channels. Those sending a non-HD signal are clear. Those
> sending an HD signal are slightly choppy. I'm guessing this is
> related to system memory, but wanted to get other opinions.
> 
> The Satellite is a model L45-S7423. It has I dual-core 1.46Ghz
> Pentium, and 1GB RAM (two 512 modules). I can upgrade to 2GB of RAM
> for under $25. But I wonder if RAM is the issue, or if processor
> speed is the issue. In the long run, this won't be the box I'd run
> Myth on eventually, so it may not be worth the expense --
> especially since this is the laptop I mentioned a couple of weeks
> ago with the damaged screen. But it is working as a test bed for me
> to get to know Myth.
> 
> Opinions are welcome.
> 

Streaming 1080i/p HD video performance will depend on
1. GPU
2. CPU/memory
3. Hard drive speed
4. network speed
5. DTV Antenna

1 and 2 should be ok on your laptop with newer linux kernels.  I have
a Free Geek Intel box running Slackware64 + XBMC 12.2 (kernel 3.2.45)
that uses the Intel Q965 chipset (GMA 3000). This GPU is a slightly
older desktop version of yours.  My CPU is Intel Core 2 duo 1.86GHz
E6300.

Funny story: 1080p HD worked ok but we noticed a few days ago (via
htop)that someone at Free Geek had disabled the 2nd core in the BIOS.
Might be something to check.

3. Your lappy is sporting a 5400 rpm SATA-150 hard drive. That could
make 1080p video a bit choppy.  Even streaming, IIRC, data gets
buffered to the hard drive.  A proper 7200 rpm SATA 2 or 3 desktop
drive will do better.

4. Network: Ive had issues streaming 1080p over wifi due to
interference and odd chipset support. It can work but takes some
tweaking of the routers, etc. Linux support for some wifi chipsets is
gimpy (broadcom).  A good Cat5 or Cat6 cable with a gigabit NIC is the
way to go (if 100 Mbps, you may need to tweak network kernel params a
bit). It you must use wifi, go with Atheros chips - far fewer packets
lost and better connections.  Look into adjusting TCP/IP parameters in
/etc/sysctl.conf (esp. TCP buffer sizes).

5. I built my own DTV antenna for grins:
http://cdn.makezine.com/make/television/04/DTV_Antenna_FINAL.pdf
I used scraps: some leftover 18 gauge Cu wire and a piece of cork
flooring. I get excellent 1080i reception of PDX stations from
Vancouver at ground level.
Another site: http://www.tvantennaplans.com/

For 1-3, a good way to test the laptop - or the real box later -
download these 1080p videos and then play them via MythTV.
http://www.bigbuckbunny.org/index.php/download/
http://www.sintel.org/download


Have Fun!
Ed






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