I’m fairly new to Tablo, and still trying to get things set up reasonably well. Along the way, I’ve experimented with 10 mbps, 8 mbps, and of course 5 mbps quality settings. I haven’t figured out how I can tell which quality a given recording was in, which makes it difficult for me to figure out if that’s a factor.
My basic problem is occasional macroblocking of motion on CBS 1080i source material. At first I thought maybe there was an issue with signal level. In order to get a better signal at the antenna, I moved the Tablo to another room and connected via Wi-Fi (802.11ac). The client of interest is a Roku 4 (also 802.11ac).
That worked fine for a while, although I still had some of the macroblocking. I tried increasing the quality level, but couldn’t see if it made a difference when viewing live (it only happens a few times an hour). But now I’m suddenly experiencing buffering during playback. Still shooting from the hip in the dark, I’m guessing I’m starting to play back recordings made at 8 or 10 mbps, and with the Wi-Fi connection, maybe that’s not going so well. So I’ve moved the Tablo back to hardwire distance, even though the signal level is lower. It still should be a pretty good signal.
Adding to my “sorceror’s apprentice” flailing: the broadcast CBS signal here is a 1080i subchannel on the 720p ABC station, which also has a 480p subchannel. The bitrate in the OTA signal is almost certainly compromised. Perhaps the macroblocking is occurring there, in which case there’s nothing I could do with the Tablo to fix it. I can’t say I’ve noticed macroblocking on the NBC 1080i signal (although maybe I just wasn’t paying attention.)
Does anyone have some wisdom to share to help me get this nailed down? It would help if I knew what quality setting a given recording was made at, but I haven’t seen that in either Roku or Android apps.
Technically, all channels are sub-channels. There’s nothing magic about the -1 sub-channel. So in your case ABC is 720p on -1 and CBS is 1080i on -2, and there something else at 480p on -3. That does sound like they might be over-compressing the video streams to fit them all in.
Do you see the macroblocking when watching that channel direct on the TV (antenna connected directly)?
If you’re getting buffering, be sure to set your streaming device (Roku, FireTV, etc) to have priority in your router settings. That really helped with mine.
No idea what the CBS subchannel looks like on my TV. Reception where the TV is located is too poor (indoor antenna). The TV is currently connected to cable, which I hope to drop come the end of this year.
Yeah, the primary subchannel is still a subchannel, but I was using the term more loosely to indicate that CBS isn’t the primary. At least you managed to figure out what I meant.
Good point on router priority, but in my case that shouldn’t matter. The only things on that Wi-Fi network are my work computer, which is offline when I’m watching TV, the Roku and the Tablo.
With the (4-tuner) Tablo hardwired in, I’m amazed how much more responsive it is hardwired. I’d expected that the Tablo’s 5 GHz 802.11n Wi-Fi would’ve been way more than sufficient for a 5 mbps data stream, but apparently it can still be a challenge. So much better with an Ethernet connection.
Last night I got flawless replay from a 1080i NBC show that I’m pretty sure was recorded in 5 mbps. I also recorded two 1080i CBS shows and one 1080i NBC show at 8 mbps, and made a note of that so when I play them back I’ll know what the issue is if they break up. Or if they buffer, but I’m confident that I won’t see buffering again with the Tablo hardwired.
Any chance you can share screenshot or short video of what you’re seeing on your end? It sounds like a fairly genuine (albeit occasional) reception issue, in which case the Tablo’s recording quality wouldn’t have much bearing. Don’t hesitate to send this directly to our team, and we can take a look.
Update: an 8 mbps CBS 1080i recording made Monday plays back without buffering now that my Tablo is hardwired, but still shows the image breaking up on motion occasionally. Since I’m pretty sure that the source stream isn’t any higher than 8 mbps, and I’m getting clean results on NBC 1080i even at 5 mbps, I’m going to assume the issue isn’t in the transcoding but rather in the source.
I’ll be watching the ABC 720p images, from the same station as the CBS subchannel, to see if they’re solid. If not, it might be an antenna issue. If ABC is clean, it’s probably over-compression of the CBS stream by the station.
Either way, it looks like it’s not the Tablo. So I’m back at 5 mbps. That gave clean results on NBC, and 8 mbps didn’t fix CBS.
