Lightbridge bug?

Ale Reynoso · Jun 20, 2017

Hi:
we´re having issues with our Inspire 2 for live feed. We went to a test with the OB truck and the engineer said it was "unacceptable". And we had to give him the reason, as the signal has a strange "breathing". Tested everything. All the setup combinations and always the same. Went from FW .240 to .330 and the same.
We started this discussion some time ago, but now we are shure it is there.
The issue is almost invisible (unless you had this engineer eye!), but if you look for it, it is there. The way we could certainly and clearly watch it is framing a "siemens star" in front of the lens. And with a big, full HD display (you will not notice it in the ipad, small monitor or cheap HD monitor) you can notice that the center of the star, the one that shows you sharp focus, "breathes", "pulses", in a cycle of two seconds aprox. We reached the conclusion that is a huge variation in bitrate that makes the image go from a sharp one to a slightly soft one. That`s all. But unacceptable anyway.
We checked it against the Inspire 1: horrible video quality, but stable...
And we say it is a bug because we checked every i2 we could find, and it is there (with the "siemens star" it shows clearly). Another way of noticing it is to lower the bitrate to the minimum.
Nobody noticed this? If the image woud be average, but stable, we wouldn´t have any issue. We need to stop this "scan" or "refresh" of the bitrate. You can notice that this "refresh" scrolls the image from top to bottom.
Has anyone noticed this and could do something?
Has anyone tried to add a suplementary video sender on the i2?
Best regards!

MedicFL1 · Jun 20, 2017

Lightbridge 2 = broadcast standard output of 720p/59.94fps and 1080i/50fps.
I've seen the Titan conquer discussed with Ralph at fly high quoted as a reference in other posts.
If that helps at all?

Shawn Esplin · Jun 20, 2017

It could be the codec they're using or the way they're using it. When using a lossy compression format for video, there are keyframes where the entire image is recorded, then (unless you set every frame to be a key frame) just the changing parts of the image are recorded for subsequent frames until the next keyframe. This can potentially result in visible degradation of the image over that time period with a return to clarity as it hits the next keyframe. That sounds to me like what you're seeing.

DJI's newer transmission systems have a much greater range, and it's very possible that they're just sending less information to keep a stable image at a greater distance. So you can ask them about it but (if they give you an answer) they might just say "it's not a bug, it's a feature".

MedicFL1 · Jun 20, 2017

The fact that it's interlaced along with key frames, codec and actual signal loss, all seem to be factors pointed out by others as well.

Ale Reynoso · Jun 21, 2017

Thanks!!
I will search Titan Conquer and see what I could find

Ale Reynoso · Jun 23, 2017

skybandit · Jun 24, 2017

Interesting and thanks for posting that video. This is only for live feed? You haven't noticed this issue recording direct to card?

Ale Reynoso · Jun 24, 2017

Only noticed it in the HDMI output, but had not made a "science test" in the H264 files. As it looks like a bitrate variation issue, higher bitrates could just hide it perfectly I think.
And we wen´t to the DJI representative saying "if ours is faulty, then just give us a new one"... but every i2 he had in the shop made the same thing, so we are assuming is a design fact or a bug.

Buzzcam · Jun 26, 2017

skybandit said:
Interesting and thanks for posting that video. This is only for live feed? You haven't noticed this issue recording direct to card?

We have done some extensive testing with recording simultaneously on the bird and of the hdmi port. He results are chalk and cheese. There is nothing wrong with the recording on the bird, the hdmi output is less then average and unusable for live broadcasting.

Buzzcam · Jun 26, 2017

IMHO DJI has misled the consumer by stating it was a broadcast ready device. I believe they were talking about social media broadcast like YouTube, Facebook etc. Not live to air TV broadcasts HD or otherwise. This would be seen as a dirty marketing trick, but being as large as they are now, they would just not give a hoot.
Just my to cents worth.
BTW, I have posted about this issue a few times, but have seen no response of any DJI team members, which probably proves me right....

Ale Reynoso · Jun 26, 2017

Buzzcam said:
IMHO DJI has misled the consumer by stating it was a broadcast ready device. I believe they were talking about social media broadcast like YouTube, Facebook etc. Not live to air TV broadcasts HD or otherwise. This would be seen as a dirty marketing trick, but being as large as they are now, they would just not give a hoot.
Just my to cents worth.
BTW, I have posted about this issue a few times, but have seen no response of any DJI team members, which probably proves me right....

I was asked for a video sample and as soon as I published it, no DJI team member answered...

Shawn Esplin · Jun 26, 2017

Buzzcam said:
IMHO DJI has misled the consumer by stating it was a broadcast ready device. I believe they were talking about social media broadcast like YouTube, Facebook etc. Not live to air TV broadcasts HD or otherwise. This would be seen as a dirty marketing trick, but being as large as they are now, they would just not give a hoot.
Just my to cents worth.
BTW, I have posted about this issue a few times, but have seen no response of any DJI team members, which probably proves me right....

With the formats they used for it (1080i50 I think was one? That and 720p60 maybe?) it seems to me that they *do* intend it to be for TV broadcast. I have also seen a *lot* of lower quality live and even pre-recorded videos on TV news, including the big stations.

That doesn't mean you have to find it acceptable for your purposes, and if I saw it on a TV screen when I wasn't looking for it I'm not sure if I'd notice or not, but I think a lot of people apply different standards for broadcast quality to live footage vs pre-recorded footage and are generally willing to compromise if the only source they have for some newsworthy footage is low quality.

Buzzcam · Jun 26, 2017

Shawn Esplin said:
With the formats they used for it (1080i50 I think was one? That and 720p60 maybe?) it seems to me that they *do* intend it to be for TV broadcast. I have also seen a *lot* of lower quality live and even pre-recorded videos on TV news, including the big stations.

That doesn't mean you have to find it acceptable for your purposes, and if I saw it on a TV screen when I wasn't looking for it I'm not sure if I'd notice or not, but I think a lot of people apply different standards for broadcast quality to live footage vs pre-recorded footage and are generally willing to compromise if the only source they have for some newsworthy footage is low quality.

I have also seen footage on some news services that came straight of the I2 HDMI port, but that's news. They do get their footage from odd sources and deal with it. We cover live sporting events that go to major networks and pay per view. If I saw "that" standard on ppv I would be less then impressed. Any operator, in our world, would not be satisfied with the service we provide if the quality we get from the I2 was the best we could give. We are now flying a M600pro with a Microlite Downlink and even though the latency is long, the picture quality is mile ahead of anything DJI can (or is willing to) produce.

Shawn Esplin · Jun 28, 2017

Good to know; I don't watch a lot of sports so I didn't think about that application. Even if they think they need to compromise quality for range, I wish they'd at least give a more solid transmission when it's 50 yards rather than 2 miles away.

Ale Reynoso · Jun 28, 2017

Has anyone checked the latest FW?
It says something about transmission image quality
And can someone please check and tell us if every i2 has the issue we documented in the video?
To see if it´s just a group of i2 (every i2 we tested did it) or all of them

cvanhoose · Jun 29, 2017

I thought I responded to you previously, I do not have this issue with the HDMI output. Solid connection with 1080i@60 to a LIVEu backpack. Also solid connection to blackmagic capture cards and Sony xbr monitors.
My I2 has a build date of Jan.27th

Ale Reynoso · Jun 29, 2017

Sorry if I meant not to reading you cvanhoose. I´m trying to get different opinions. I asked several i2 owners here, received the answer "never had a problem with my i2" and when we did some test with their equipment, they had the same issue I documented in the video. Some people just did not noticed it. It is very specific and subtle. A lot of people is feedind this kind of signal to OB trucks and the engineers are using just as it is. This not means this issue doesn´t exist.
Moderator: I was trying to be clearer and clean in the post. With a video sample. Aiming to a DJI representative. There I left a dropbox file, a Vimeo video and a Youtube video. They are not in this post. Just that.
I will add them here if it is what you require.

Ale Reynoso · Jun 29, 2017

We tried several combinations of converters as we are asked to send an SDI signal. Black Magic mini converter, Decimator, Atomos. Even a TV Logic monitor as converter directly from the RC HDMI (tried master and slave). The issue is always there.
We played with all possible combinations. Transmission 1080 and 720, and the output as 1080 24, 25, 30 P, 50 and 60i, 720 24, 25, 30 P. Always there
Wich FW are you running ?
The video I uploaded was recorder from the HDMI output via an Atomos Shogun in Apple Prores 422

The Editor · Jun 30, 2017

Ale Reynoso said:
Sorry if I meant not to reading you cvanhoose. I´m trying to get different opinions. I asked several i2 owners here, received the answer "never had a problem with my i2" and when we did some test with their equipment, they had the same issue I documented in the video. Some people just did not noticed it. It is very specific and subtle. A lot of people is feedind this kind of signal to OB trucks and the engineers are using just as it is. This not means this issue doesn´t exist.
Moderator: I was trying to be clearer and clean in the post. With a video sample. Aiming to a DJI representative. There I left a dropbox file, a Vimeo video and a Youtube video. They are not in this post. Just that.
I will add them here if it is what you require.

Yes - please keep this thread going (rather than start another which I have closed).
Also, please bear in mind this forum is a publically owned and managed community that has no affiliation to or with DJI.
Occasionally Ed or Ken will pop by but they do not actively monitor or regularly contribute to this board.
You will probably get better response from DJI's own forum or from their tech/R&D areas.

As an aside - yes the HDMI o/p is garbage from the remotes and always has been. If you look over the forum I have always said this from day one. Don't forget that the HDMI protocol/interface is not a professional termination it is purely a consumer connection and I have seen many issues with engineers attempting to get a decent feed from the HDMI port. This ranges from the issues you are having to sync and handshake/re-link errors.

I wish you luck getting DJI to respond....... I wouldn't hold your breath