4K video from VRD plays jerky.

MozartMan

Member
Hi,

I got Sony Alpha a6500 camera few days ago and playing with 4K video recording. I am using 4K mode in XAVC-S at 30p and 60 Mbps bitrate. I can load MP4 video file produced by a6500 into VRD without any problem. I do simple cuts at the beginning and at the end of the file.

Then I tried to output video file in MP4 and M2TS format, but file plays back with jerkiness, especially on my Samsung UND player. And I enabled 4K output in Manual options menu.

Am I missing something? What parameters do I need to tweak in order for the video to play smooth after processing in VRD?

Thanks
 

MozartMan

Member
Dan,

Here is info:

Original source file from Sony a6500:

General
Complete name : E:\z_a6500\Video\4K\02\0002.MP4
Format : XAVC
Codec ID : XAVC (XAVC/mp42/iso2)
File size : 156 MiB
Duration : 24 s 24 ms
Overall bit rate mode : Variable
Overall bit rate : 54.5 Mb/s
Encoded date : UTC 2018-05-03 21:30:40
Tagged date : UTC 2018-05-03 21:30:40

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L5.1
Format settings : CABAC / 2 Ref Frames
Format settings, CABAC : Yes
Format settings, RefFrames : 2 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 24 s 24 ms
Bit rate mode : Variable
Bit rate : 51.7 Mb/s
Maximum bit rate : 60.0 Mb/s
Width : 3 840 pixels
Height : 2 160 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 29.970 (30000/1001) FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.208
Stream size : 148 MiB (95%)
Encoded date : UTC 2018-05-03 21:30:40
Tagged date : UTC 2018-05-03 21:30:40
Color range : Limited
Color primaries : BT.709
Transfer characteristics : xvYCC
Matrix coefficients : BT.709

Audio
ID : 2
Format : PCM
Format settings : Big / Signed
Codec ID : twos
Duration : 24 s 24 ms
Bit rate mode : Constant
Bit rate : 1 536 kb/s
Channel(s) : 2 channels
Sampling rate : 48.0 kHz
Bit depth : 16 bits
Stream size : 4.40 MiB (3%)
Encoded date : UTC 2018-05-03 21:30:40
Tagged date : UTC 2018-05-03 21:30:40

Other
Type : meta
Duration : 24 s 24 ms


Output file from VRD:

General
Complete name : E:\z_a6500\Video\4K\02\0002---VRD.mp4
Format : MPEG-4
Format profile : Base Media
Codec ID : isom (isom/iso2/avc1/mp41)
File size : 135 MiB
Duration : 21 s 422 ms
Overall bit rate mode : Variable
Overall bit rate : 53.0 Mb/s
Writing application : VideoReDo (Lavf56.25.101)

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L5.1
Format settings : CABAC / 2 Ref Frames
Format settings, CABAC : Yes
Format settings, RefFram : 2 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 21 s 422 ms
Bit rate mode : Variable
Bit rate : 52.7 Mb/s
Maximum bit rate : 60.0 Mb/s
Width : 3 840 pixels
Height : 2 160 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 29.970 (30000/1001) FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.212
Stream size : 135 MiB (100%)
Color range : Limited
Color primaries : BT.709
Transfer characteristics : xvYCC
Matrix coefficients : BT.709

Audio
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Codec ID : mp4a-40-2
Duration : 21 s 419 ms
Duration_LastFrame : -21 ms
Bit rate mode : Variable
Bit rate : 256 kb/s
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 SPF)
Compression mod : Lossy
Stream size : 663 KiB (0%)
Default : Yes
Alternate group : 1
 

Dan203

Senior Developer
Staff member
Try only cutting the end, but not the beginning. Does that have any effect? (just wondering if our recoded frames are causing an issue)

As another test go into the Advanced section of the profile and in the MP4 section disable the option for "Keep SPS/PPS in video frames". That could also, maybe, cause an issue.

Other then that the only major difference is the audio format. Your TV doesn't have an issue with AAC audio does it?
 

MozartMan

Member
Try only cutting the end, but not the beginning. Does that have any effect? (just wondering if our recoded frames are causing an issue)
OK. I loaded original Sony file into VRD and made two new files - one without any cuts, one with the cut at the end. Both files played good, like original Sony file.
I guess cut at the beginning is causing this issue.

As another test go into the Advanced section of the profile and in the MP4 section disable the option for "Keep SPS/PPS in video frames". That could also, maybe, cause an issue.
Samsung player could not load the file with this setting.

Other then that the only major difference is the audio format. Your TV doesn't have an issue with AAC audio does it?
No.
 

Dan203

Senior Developer
Staff member
The first and second test confirm that our encoder isn't matching parameters of the source file exactly. This is rare, but happens occasionally. Does your TV support TS files? If it does try one of those. It might be able to handle the transition from the recoded frames to the original frames better in a TS then an MP4.
 
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