I came across this in another thread, and it triggered a suppressed concern and requirement I had about Tablo recordings.
My main concern is regarding the fact that Tablo has a single quality setting for all recordings.
Now it appears that it will transcode broadcasts of lesser quality into higher formats, merely to fill the requirement? What happens if I try to record some of those stations broadcasting at 480p?
Why can Tablo not simply record programs broadcast at their original signal quality?
Why can the recording quality not be a default that we can set individually lower (or higher) for recordings that may warrant it? For instance, I really don’t care of my news broadcast is in lower quality recording, but I do want to see sports (eg. Golf) in the highest possible resolution. To do that everything has to be at high resolution, chewing up bandwidth and loading the WiFi in my home needlessly, as well as taking up unwarranted amounts of storage space on my hard drive. This seems to be one of the biggest oversights in the current Tablo firmware design.
Because OTA broadcasts are MPEG-2, and the Tablo HAS to trancode those to something else for streaming. There are almost no streamer boxes or devices out there that can decode MPEG-2. Since it has to transcode, it has to have a target data rate to trancode to. But data rate is not the same as signal format.
Yes, it could probably be smarter about the data rate to use depending on the original signal format. That’s a worthwhile feature request.
Tablo is a streaming device. it’s not a direct attached to the TV HDMI device (direct attached tuner).
So… it can never deliver original broadcast record quality (well if it did, the files would be larger than the original). And the original broacast type is mpeg2 ts, which isn’t easily streamable even to the few devices that could natively handle it.
With that said, it might be possible for Tablo to do variable recording quality by “type” or even by specific scheduled recording. I think it’s a reasonable feature request.
My Tablo records SD channels at their native quality. I’m examining several programs recorded on PBS 8.2 (an entirely SD channel) and their properties are 704 x 480 at a bit rate one third that of HD. My HD programs from PBS 8.1 (an entirely HD channel) are recorded at 1920 x 1080 with three times the bit rate of SD. So there is Tablo variability in recording different streams. On another SD channel (FOX 5.2) the Tablo records at even lower settings (80% of 8.2 because the Movies channel transmits very low quality film settings and bit rates). All of these files, when pulled off the Tablo can be internally examined by a variety of video editors. Their sizes all vary from megabytes to gigabytes.
1080i is the highest quality HD recording available. At this setting Tablo will record all broadcasts coming from your local towers at full quality. Broadcasts being sent to your antenna at 720p or standard definition will not be transformed to 1080i quality but will be recorded at the same 10 Mbps bandwidth which can provide a crisper overall picture.
This recording quality setting will also record broadcasts in 720p at a full 60 fps when available. Broadcasts of this nature are typically sporting events. This will result in a clearer picture during fast motion.
So no, we don’t upconvert things. The highest recording quality allows for the full broadcast quality to be preserved, no matter what quality or frame rate is broadcast.
Allowing users to set a recording quality per recording on a single tuner device wouldn’t be a huge deal. What gets really complicated (if not impossible) is when you have multiple tuners requesting recordings at several different rates. On a 2-Tuner device the logic could probably be worked out, although I’m not sure if the chip would even allow this. On a 4-Tuner device, the logic would get pretty painful.
All Kodi boxes using Kodi PVR clients can receive native MPEG-2 streams from servers. My Raspberry Pi TV tuner server software (TVHeadend) has a passthru mode that will deliver MPEG-2 streams using UPnP without any transcoding. As well Windows PVR software such as MediaPortal also have the option of streaming MPEG-2 to a Kodi client.
I had to buy an MPEG-2 hardware processing license ($3) from the Pi Foundation to use GPU cores for MPEG-2 decoding\encoding otherwise MPEG-2 processing in software is terrible. However MPEG-2 processing, transmission and delivery is a b*tch with heavy use of processor and memory resources. Better to transcode and whittle a stream to a third of its size. At least ATSC 3.0 will have MP4 transmission OTA. Recording and storing 10 GB .ts streams eats up drive space fast…