[rykr]

I'm only seeing this on some channels. I watched recorded shows from AMC, ABC, NBC, and CBS tonight. All of them seem fine except the ones from CBS which show quite a bit of jitters. The video is 'shaky'.

I tried turning on the dynamic refresh rate matching but didn't help. Using codecinfo I was able to see that all the videos that play well are fr 59.94 with a bit rate of like 8.5 Mbps. The cbs (jittery) ones were 29.97 with bitrate of like 13.5 Mbps.

I played the same videos on nexus player with no jitters at all.

Any idea what's going on here?

Thanks!

[noggin]

I'm guessing the CBS stuff is reporting 29.97 as it is 1080i interlaced (which will be a 59.94 field rate/29.97 frame rate) - and some systems report frame rates not field rates with interlaced sources.

The stuff reported as 59.94 is almost certainly 720p (Fox, ABC?) and progressive.

However in most regions NBC is also a 1080i service - though some affiliates cross-convert to 720p to reduce bandwidth I believe. (Though O&Os don't) PBS is also usually 1080i, though again some stations cross convert.

Another cause could be the way 23.976 content is handled by the MPEG2 encoders used by your local stations. 23.976p content (i.e. most scripted drama and comedy) is carried in a 29.97i interlaced stream using 3:2 pulldown - where one source frame is shown for 3 fields, the next for 2 fields. Some MPEG2 encoders send all 5 fields, others send just 4 with a repeat field flag (saying effectively - I sent that field already, just repeat it please) This can cause issues in some situations.

Additionally you also have to deinterlace 3:2 content in 29.97i video a lot more carefully than in 59.94p (which doesn't need deinterlacing)

Oh - and CBS, as you can see, often runs at higher bitrates than other broadcasters in the US, so you may be just hitting a bandwidth limit.

For info - in the US the following broadcaster split is usually (though not always) observed as these are the network formats :

1080i : NBC, CBS, PBS
720p : ABC, Fox

[rykr]

Noggin

Lots of good info there. Are saying the software decoding of the fire tv can't handle it.?

[rykr]

From what I can tell both the nexus player and fire TV are using ffmpeg for decoding and yet nexus player has no issue with the CBS content.

[rykr]

Correction, it's using amc-mpeg2 on the nexus. So I guess the nexus is doing hardware decoding while fire is using ffmpeg.

[rykr]

Couple of questions.

1. Is amc-mpeg2 some type of hardware decoder?
2. Is the use of ff-mpeg2 on the Fire TV a function of Kodi? Meaning could a future update of Kodi start using a hardware decoder that is on the fire tv? I find it hard to believe that a hw decoder is not there with it being able to do 4k.

Thanks

[noggin]

Couple of questions.
1. Is amc-mpeg2 some type of hardware decoder?

Probably - there are multiple approaches to Android video decoding ISTR - based on chipsets. AIUI the Google Nexus Player is based on an Intel Atom SoC, but the FireTV is based on a Qualcomm ARM-based device. The video replay route used on one may be different to another.

2. Is the use of ff-mpeg2 on the Fire TV a function of Kodi? Meaning could a future update of Kodi start using a hardware decoder that is on the fire tv? I find it hard to believe that a hw decoder is not there with it being able to do 4k.

Possibly - I think there are ffmpeg builds on some platforms that themselves use hardware acceleration, but it sounds like this isn't the case?

The real issue is that Android on Kodi has changed direction I think. Originally the Android APIs for video acceleration were close to non-existent so early Android builds included hardware specific video replay solutions to access the hardware directly, or independently of the official Android APIs. This meant that Android Kodi was pretty fragmented with different modules to support different types of hardware - AMLogic, Intel etc.

However with newer releases of Android, Google improved the video playback APIs, meaning it was possible to use APIs and avoid fragmentation. I believe this is the route that Kodi for Android now favours, so newer SoCs don't have specific video replay support, and instead use the standard Google Android solutions.

I think that Google may not support MPEG2 via this route, though, as it is an old codec that isn't found on web-based content for streaming, and is really only found on DVD and Broadcast TV that are still using standards set nearly two decades ago.

As a result whilst H264 and newer codecs get hardware acceleration, MPEG2 falls back to ffmpeg software acceleration? If Kodi doesn't include a workaround to access the FireTV's MPEG2 acceleration, or indeed if the FireTV doesn't have or expose MPEG2 acceleration, then this may be as good as you get. This is where Linux solutions have a bit of a benefit I guess.

Koying - please feel free to correct me...

[noggin]

Noggin

Lots of good info there. Are saying the software decoding of the fire tv can't handle it.?

Software decoding of 1080i will require both decoding of 1920x1080/29.97i video streams (62Mpixels/s) AND deinterlacing. Software decoding of 720p will require decoding of 1280x720/59.94p streams (55Mpixels/s) but no de-interlacing. 720p is thus less CPU intensive for software decoding, as de-interlacing is quite a CPU intensive function if being done in software.

[wrxtasy]

Even with the FireTV1 you could never have Hardware decoding switched on and get even basic Bob Deinterlacing from 1080i streams.
Turn Hardware decoding off, and you get ff-mpeg2 software decoding, stuttering with 1080i and basic Bob Deinterlacing.

Koying took the FireTV1 as far as he could to even get basic Bob deinterlacing working I believe.

FireTV users have to realise that they are dealing with a closed secure Firmware device built for streaming DRM video from Amazon. Amazon are openly hostile to Open Source Software like Kodi as it competes with their DRM streaming business model.

Firmware updates for Kodi compatibility are the last thing Amazon will provide to Kodi users.

[David248]

I've noticed this behavior with my Kodi 15.2 setup on a FireTV as well with my CBS feed, which is coming from the Detroit WWJ-TV broadcast, received by a HD HomeRun Extend, which is trans-coding to H.264 using the Heavy profile, so MPEG-2 decoding should be out of the picture. Another interesting point, I have both a Fire TV Gen 1 & Gen 2, and the issue seems to be much worse on the Gen 2 (4K version) of the Fire TV, which make me wonder if it has something to do with the Android OS version?

Other 1080i stations such as NBC don't seem to have the issue. I notice some glitching on CW, which is also 1080i, but not like the jitters I see on CBS.