Curious issue with b-references in Elemental

Blue_MiSfit · 5th June 2015, 19:13

Hello folks!

Gosh, it's been awhile since I've posted...

In any case, I've been using lots of commercial encoders these days in my professional life, for a variety of reasons. One of these encoders is Elemental - specifically their Elemental Live product that takes live inputs from HD-SDI, MPEG-TS over IP, RTMP etc and generates one or more GOP aligned outputs packaged in one or more ways.

Elemental has been continually developing their product, and they recently added support for reference B-Frames. This seems to work fine almost everywhere, including hardware decoders on iOS devices, and LAV decoding in MPC-HC. However, VLC shows strange block artifacts on decode!

I'm wondering if one of the clever folks here with stream analysis tools could give me any insight as to why this is happening? Here's a short test clip using Big Buck Bunny - Sunflower in 720p59.94 at 2 Mbps.

http://www.mediafire.com/watch/s7685.../test_bref.mp4

For those familiar with Elemental, this stream was encoded with their GPU encoder.

sneaker_ger · 5th June 2015, 19:22

Quote:

Originally Posted by Blue_MiSfit

LAV decoding in MPC-HC

LAV software has same problem. (I.e. ffmpeg)

videoh · 5th June 2015, 20:19

Looks OK with DGDecNV.

nevcairiel · 5th June 2015, 21:31

All Hardware Decoders in LAV or otherwise seem to handle it fine, so the bitstream seems alright.
I would recommend to simply report it as a bug to ffmpeg, H264 corruption bugs are usually fixed rather quickly (http://ffmpeg.org/bugreports.html)

Blue_MiSfit · 5th June 2015, 23:09

Ah! I see the same issue! I thought my LAV was set to software but it was set to cuvid

I'll whine at the ffmpeg guys.

Blue_MiSfit · 5th June 2015, 23:45

Also verified that latest ffplay exhibits the same issue.

Ticket created with ffmpeg trac

https://trac.ffmpeg.org/ticket/4596

benwaggoner · 6th June 2015, 18:53

You should probably report to Elemental as well. They have some of the best support in the business.

Blue_MiSfit · 6th June 2015, 20:03

That's the first thing I did, Ben

Their support really is first class.

nevcairiel · 9th June 2015, 11:32

The issue was fixed in ffmpeg this morning, and will be in the next LAV nightly build. Now only a question of VLC updating their ffmpeg eventually.

Blue_MiSfit · 9th June 2015, 17:14

I saw the same thing. Does VLC lag behind, generally speaking?

Tried with ffplay built today but still no-go. I'm guessing the build was made before the fix was implemented. I'll try again tomorrow.

benwaggoner · 12th June 2015, 00:02

Quote:

Originally Posted by nevcairiel

The issue was fixed in ffmpeg this morning, and will be in the next LAV nightly build. Now only a question of VLC updating their ffmpeg eventually.

What was the bug?

nevcairiel · 12th June 2015, 00:15

Quote:

Originally Posted by benwaggoner

What was the bug?

The SSSE3 optimized bi-weighting code didn't properly handle a corner case in the weightings. The code in question was from like 2010, surprising that never occurred before.

Blue_MiSfit · 12th June 2015, 06:33

Verified latest ffplay can decode this sample perfectly.

5th June 2015, 19:13	#1 \| Link
Blue_MiSfit Derek Prestegard IRL Join Date: Nov 2003 Location: Los Angeles Posts: 5,989	Curious issue with b-references in Elemental Hello folks! Gosh, it's been awhile since I've posted... In any case, I've been using lots of commercial encoders these days in my professional life, for a variety of reasons. One of these encoders is Elemental - specifically their Elemental Live product that takes live inputs from HD-SDI, MPEG-TS over IP, RTMP etc and generates one or more GOP aligned outputs packaged in one or more ways. Elemental has been continually developing their product, and they recently added support for reference B-Frames. This seems to work fine almost everywhere, including hardware decoders on iOS devices, and LAV decoding in MPC-HC. However, VLC shows strange block artifacts on decode! I'm wondering if one of the clever folks here with stream analysis tools could give me any insight as to why this is happening? Here's a short test clip using Big Buck Bunny - Sunflower in 720p59.94 at 2 Mbps. http://www.mediafire.com/watch/s7685.../test_bref.mp4 For those familiar with Elemental, this stream was encoded with their GPU encoder.

5th June 2015, 21:31	#4 \| Link
nevcairiel Registered Developer Join Date: Mar 2010 Location: Hamburg/Germany Posts: 10,348	All Hardware Decoders in LAV or otherwise seem to handle it fine, so the bitstream seems alright. I would recommend to simply report it as a bug to ffmpeg, H264 corruption bugs are usually fixed rather quickly (http://ffmpeg.org/bugreports.html) __________________ LAV Filters - open source ffmpeg based media splitter and decoders

5th June 2015, 23:45	#6 \| Link
Blue_MiSfit Derek Prestegard IRL Join Date: Nov 2003 Location: Los Angeles Posts: 5,989	Also verified that latest ffplay exhibits the same issue. Ticket created with ffmpeg trac https://trac.ffmpeg.org/ticket/4596 Last edited by Blue_MiSfit; 5th June 2015 at 23:52.

6th June 2015, 18:53	#7 \| Link
benwaggoner Moderator Join Date: Jan 2006 Location: Portland, OR Posts: 4,771	You should probably report to Elemental as well. They have some of the best support in the business. __________________ Ben Waggoner Principal Video Specialist, Amazon Prime Video My Compression Book

9th June 2015, 11:32	#9 \| Link
nevcairiel Registered Developer Join Date: Mar 2010 Location: Hamburg/Germany Posts: 10,348	The issue was fixed in ffmpeg this morning, and will be in the next LAV nightly build. Now only a question of VLC updating their ffmpeg eventually. __________________ LAV Filters - open source ffmpeg based media splitter and decoders

5th June 2015, 20:19	#3 \| Link
videoh Useful n00b Join Date: Jul 2014 Posts: 1,667	Looks OK with DGDecNV.

5th June 2015, 23:09	#5 \| Link
Blue_MiSfit Derek Prestegard IRL Join Date: Nov 2003 Location: Los Angeles Posts: 5,989	Ah! I see the same issue! I thought my LAV was set to software but it was set to cuvid I'll whine at the ffmpeg guys.

6th June 2015, 20:03	#8 \| Link
Blue_MiSfit Derek Prestegard IRL Join Date: Nov 2003 Location: Los Angeles Posts: 5,989	That's the first thing I did, Ben Their support really is first class.

9th June 2015, 17:14	#10 \| Link
Blue_MiSfit Derek Prestegard IRL Join Date: Nov 2003 Location: Los Angeles Posts: 5,989	I saw the same thing. Does VLC lag behind, generally speaking? Tried with ffplay built today but still no-go. I'm guessing the build was made before the fix was implemented. I'll try again tomorrow. Last edited by Blue_MiSfit; 9th June 2015 at 17:21.

12th June 2015, 06:33	#13 \| Link
Blue_MiSfit Derek Prestegard IRL Join Date: Nov 2003 Location: Los Angeles Posts: 5,989	Verified latest ffplay can decode this sample perfectly.