TV: could not read first 2048 bytes

[dvdearden]

I'm a new user (about a week) trying to get a somewhat unusual setup working. I have the HDHomerun Extend tuner card and am running Myth backend under Mythbuntu in a Virtual Box on a Mac Mini Core Duo machine (32-bit) running OS X 10.6.8. I have the transcoding set on the HDHomerun to "Internet 540" to compensate for my relatively slow home network. Almost everything is working, but for one of the main network TV over-the-air channels I always get the "could not read first 2048 bytes" error when I try to watch live TV, and "recording unavailable" (with nothing being saved to disk) when I try to watch a recording from that channel. However, the hdhomerun_view app (run Mac-native from a different machine) works fine on that channel, as does VLC run from the Mac Mini. So this must be a problem in my setup somehow. Any advice?

David

[pvr4me]

Are you saying that you can record/watch _all_ channels except one? What signal strength/quality does the HDHomerun_view app report versus channels that you can receive. Did you have to do anything special to add that channel or was it picked up normally by the channel scanner? Is the broadcast tower physically located in the same direction as other channels that you can receive?

Is there some reason that you want to run a VM rather than running MythBackend directly under OS X 10.6.8? See:

https://www.mythtv.org/wiki/MacPorts

Craig

[dvdearden]

Craig,

Thanks for your reply. Yes, recording and watching work on all the other channels as far as I can tell. They work for the other subchannels on the same channel as the problematic one (the problem one is HD, the subchannels are not). The signal strength and quality for this channel seems about the same as any of the others, and stronger than some that I can receive. This channel was picked up normally with the rest on the channel scan, and the broadcast towers for nearly all the channels I get are on the same mountain about 50 miles away (I'm definitely right on the edge of being able to pick all of them up, but if my antenna is pointed right it works with some occasional pixelation).

The reason I'm running a VM is that my hardware is the old 32-bit core duo (not core 2 duo) Mac Mini. I first tried installing an OSX version of Myth 0.24, which I believe is the most recent version compiled for 32-bit OSX, but couldn't get SchedulesDirect working with that. I found several compilations of Myth 0.27 for 32-bit Ubuntu, so that's why I decided to use Mythbuntu 14.04 with Myth 0.27 in a VM. I found the VirtualBox and Mythbuntu installs to be pretty easy, but certainly I'd prefer to run the backend OSX-native with the MacPorts version if I could find a version that works on this old Mac Mini and works with SchedulesDirect. I used MacPorts to install Myth 0.27.4 on my new MacBook Pro and that works well (but I haven't checked out the problematic channel with that system-I ought to try that); however, I can't use the MacBook Pro for the backend because it doesn't stay on at home all the time; it's my work machine and goes with me everywhere.

Thanks,
David

[yawlhoo]

I have no idea if the following is really relevant to your setup.

Years ago I had a situation where everything worked great on my system except the first 30 sec or so of the recording of one single channel went missing, just about every time (more or less daily, the program was the news.) I contacted Silicon Dust, because I thought the problem must be with my HDHomeRun tuner.

Long story short, they helped me figure it out, it was the first signs of the hard drive going bad. I was pretty skeptical, but I replaced the hard drive, and lo and behold: the problem went away completely!

Incidentally, this helped convince me Silicon Dust is a great company to do business with!

FWIW.

[pvr4me]

Craig,

Thanks for your reply. Yes, recording and watching work on all the other channels as far as I can tell. They work for the other subchannels on the same channel as the problematic one (the problem one is HD, the subchannels are not). The signal strength and quality for this channel seems about the same as any of the others, and stronger than some that I can receive. This channel was picked up normally with the rest on the channel scan, and the broadcast towers for nearly all the channels I get are on the same mountain about 50 miles away (I'm definitely right on the edge of being able to pick all of them up, but if my antenna is pointed right it works with some occasional pixelation).

OK, I think the best bet to debug this is to see the backend logs. I suggest you restart the VM and try to record something from a known-good channel AND the bad one. Find the backend log and attach it here.

The reason I'm running a VM is that my hardware is the old 32-bit core duo (not core 2 duo) Mac Mini. I first tried installing an OSX version of Myth 0.24, which I believe is the most recent version compiled for 32-bit OSX, but couldn't get SchedulesDirect working with that. I found several compilations of Myth 0.27 for 32-bit Ubuntu, so that's why I decided to use Mythbuntu 14.04 with Myth 0.27 in a VM. I found the VirtualBox and Mythbuntu installs to be pretty easy, but certainly I'd prefer to run the backend OSX-native with the MacPorts version if I could find a version that works on this old Mac Mini and works with SchedulesDirect. I used MacPorts to install Myth 0.27.4 on my new MacBook Pro and that works well (but I haven't checked out the problematic channel with that system-I ought to try that); however, I can't use the MacBook Pro for the backend because it doesn't stay on at home all the time; it's my work machine and goes with me everywhere.

Ah. I gave up trying to build Myth for 32-bit OS X a couple of years ago. There are some critical bits of the underlying ffmpeg code that are written in assembler that became unusable in that environment. There are high-level code fallbacks that will build--but they run too slowly on those old Macs to be usable. Trying to fix it was _way_ beyond my pay grade. I think jya made it work for a version or two but I don't remember the details.

BTW, the Core Duo Minis were released in 2006. I think the newest version of OS X you can run is 10.7.5 so you haven't been getting security updates for a few years. You might either trade up to a newer Mini or wipe it and install Linux on the bare hardware.

Craig

[dvdearden]

I have a little more data. I see the exact same problem when running the MacPorts backend (0.27.4) on my new MacBook Pro: channel 5.1 will not play or record, although the others do. So this probably is not a problem specific to running the backend on a VM on an old computer, because I see the same thing when running Mac-native on an up-to-date computer. Finally, it occurred to me to change the transcode configuration on the HDHomerun using the "myhdhomerun.com" interface. If I turn the hardware transcoding off, everything works although there is some stuttering due to heavy network traffic. The problem happens when I use any of the hardware transcoding settings. So I guess if I want to record on that particular channel, I have to make sure the HDHomerun hardware transcoding is turned off. Kind of weird, but at least there is a workaround of sorts.

David

[pvr4me]

Aha! It appears that you have the same problem as another user. You can see the gory details at:

viewtopic.php?f=26&t=775

PLEASE, report this to SiliconDust. They have the expertise to determine what is different about the broadcaster's stream viz their transcode settings. Hopefully they just need to tweak something to prevent these kinds of bizarre problems.

Craig

[dvdearden]

Craig,

Thanks for your help. Yes, that sounds like the same problem. I'll report this to SiliconDust.

David