Broadcast .mxf File

[chris319]

For your interest, here is the MediaInfo information from one of the .mxf files we broadcast on our U.S. TV station.

General
Complete name                            : Title.mxf
Format                                   : MXF
Commercial name                          : XDCAM HD 35
Format version                           : 1.3
Format profile                           : OP-1a
Format settings                          : Closed / Complete
File size                                : 180 MiB
Duration                                 : 39 s 706 ms
Overall bit rate mode                    : Variable
Overall bit rate                         : 38.0 Mb/s
Encoded date                             : 2019-02-25 16:30:45.208
Writing application                      : Grass Valley K.K. EDIUS 8.2.0.312

Video
ID                                       : 2
Format                                   : MPEG Video
Commercial name                          : XDCAM HD 35
Format version                           : Version 2
Format profile                           : Main@High
Format settings                          : CustomMatrix / BVOP
Format settings, BVOP                    : Yes
Format settings, Matrix                  : Custom
Format settings, GOP                     : M=3, N=15
Format settings, wrapping mode           : Frame
Codec ID                                 : 0D01030102046001-0401020201030300
Duration                                 : 39 s 706 ms
Bit rate mode                            : Variable
Bit rate                                 : 35.0 Mb/s
Width                                    : 1 280 pixels
Height                                   : 720 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 59.940 (60000/1001) FPS
Standard                                 : Component
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 0.634
Time code of first frame                 : 00:00:00;00
Time code source                         : Group of pictures header
GOP, Open/Closed                         : Open
GOP, Open/Closed of first frame          : Closed
Stream size                              : 166 MiB (92%)
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709

Audio #1
ID                                       : 3
Format                                   : PCM
Format settings                          : Little
Format settings, wrapping mode           : Frame (AES)
Codec ID                                 : 0D01030102060300
Duration                                 : 39 s 706 ms
Bit rate mode                            : Constant
Bit rate                                 : 768 kb/s
Channel(s)                               : 1 channel
Sampling rate                            : 48.0 kHz
Frame rate                               : 59.940 FPS (800.8 SPF)
Bit depth                                : 16 bits
Stream size                              : 3.64 MiB (2%)
Locked                                   : Yes

Audio #2
ID                                       : 4
Format                                   : PCM
Format settings                          : Little
Format settings, wrapping mode           : Frame (AES)
Codec ID                                 : 0D01030102060300
Duration                                 : 39 s 706 ms
Bit rate mode                            : Constant
Bit rate                                 : 768 kb/s
Channel(s)                               : 1 channel
Sampling rate                            : 48.0 kHz
Frame rate                               : 59.940 FPS (800.8 SPF)
Bit depth                                : 16 bits
Stream size                              : 3.64 MiB (2%)
Locked                                   : Yes

Other #1
ID                                       : 1-Material
Type                                     : Time code
Format                                   : MXF TC
Time code of first frame                 : 00:00:00;00
Time code settings                       : Material Package
Time code, striped                       : Yes

Other #2
ID                                       : 1-Source
Type                                     : Time code
Format                                   : MXF TC
Time code of first frame                 : 00:00:00;00
Time code settings                       : Source Package
Time code, striped                       : Yes

Other #3
Type                                     : Time code
Format                                   : SMPTE TC
Muxing mode                              : SDTI
Time code of first frame                 : 00:00:00;00

[chris319]

Here is an ffmpeg command I came up with to convert an mp4 file. The high bit rate is needed to keep the levels within spec. The scale filter is to keep the colors accurate.

ffmpeg -y  -i  output.mp4  -vcodec mpeg2video  -pix_fmt yuv420p  -s 1280x720  -r 59.94  -b:v 35M  -vf  scale=out_color_matrix=bt709,lutyuv=y='clip(val,16,235)'  -acodec pcm_s16le  -ar 48000  -ac 2  output.mxf

[sneaker]

Is ffmpeg handling the audio correctly with your command or just expanding the first channel to stereo while completely discarding the second one?

https://trac.ffmpeg.org/wiki/AudioChannelManipulation#a2monostereo

[chris319]

Is ffmpeg handling the audio correctly with your command or just expanding the first channel to stereo while completely discarding the second one?

https://trac.ffmpeg.org/wiki/AudioChannelManipulation#a2monostereo

I don't know; I haven't tested that.

Would you do it differently?

[sneaker]

I would merge the two mono tracks using the "amerge" filter into a single stereo track like described in my link. I think you are doing "mono -> stereo" but should be doing "2x mono -> stereo".

[chris319]

I looked at your link.

Why wouldn't ffmpeg simply pass the one stereo pair without changing anything?

Viz.:

L -> L
R -> R

To do what you're suggesting would require two input files:

ffmpeg -i left.mp3 -i right.mp3 -filter_complex "[0:a][1:a]join=inputs=2:channel_layout=stereo[a]" -map "[a]" output.mp3

[sneaker]

Why wouldn't ffmpeg simply pass the one stereo pair without changing anything?

Because like MediaInfo it doesn't see a single stereo track, it sees 2 mono tracks. By default ffmpeg only maps one audio track.
https://trac.ffmpeg.org/wiki/Map#Default

Audio #1
ID : 3
Format : PCM
Format settings : Little
Format settings, wrapping mode : Frame (AES)
Codec ID : 0D01030102060300
Duration : 39 s 706 ms
Bit rate mode : Constant
Bit rate : 768 kb/s
Channel(s) : 1 channel
Sampling rate : 48.0 kHz
Frame rate : 59.940 FPS (800.8 SPF)
Bit depth : 16 bits
Stream size : 3.64 MiB (2%)
Locked : Yes

Audio #2
ID : 4
Format : PCM
Format settings : Little
Format settings, wrapping mode : Frame (AES)
Codec ID : 0D01030102060300
Duration : 39 s 706 ms
Bit rate mode : Constant
Bit rate : 768 kb/s
Channel(s) : 1 channel
Sampling rate : 48.0 kHz
Frame rate : 59.940 FPS (800.8 SPF)
Bit depth : 16 bits
Stream size : 3.64 MiB (2%)
Locked : Yes

To do what you're suggesting would require two input files:

No.

ffmpeg -i "whatever.mxf" -map v -filter_complex "[0:a:0][0:a:1]amerge=inputs=2[a]" -map "[a]" "output.mp4"

[poisondeathray]

I think he's starting with a MP4 with stereo audio , not a MXF with two mono audio streams

[sneaker]

Oooh. My bad. I indeed thought he wanted to convert mxf to mp4.

[chris319]

I think he's starting with a MP4 with stereo audio , not a MXF with two mono audio streams

Right.

[flashandpan007]

I thought the same as sneaker. Next time describe it with a few words what you want to do exactly, otherwise I won‘t give help anymore here. Especially from a guy who works for a tv station I can expect that.

Just look at the title - it says nothing except one format.

[chris319]

Just look at post #2 in this thread:

Here is an ffmpeg command I came up with to convert an mp4 file.

The input file is mp4; the output file is mxf. Surely you can figure it out from that.

[chris319]

What concerns me is that the Y levels change if the video bit rate is reduced.

[Cornucopia]

If the bitrate is reduced, the quantizer changes. When the quantizer changes, it makes rougher guesses based on more constrained info - some of which includes individual Y, U, or V values. You should expect this when bitrate is reduced...they're called artifacts.

Scott

[chris319]

If the bitrate is reduced, the quantizer changes. When the quantizer changes, it makes rougher guesses based on more constrained info - some of which includes individual Y, U, or V values. You should expect this when bitrate is reduced...they're called artifacts.

Scott

Think it would help to shoot at a lower bit rate? Right now I'm shooting at 50 Mbps.

[Cornucopia]

You said, in post #2, "high bitrate is needed to keep levels within spec". What spec are you referring to? That spec should determine what you should be doing. Considering your source is 35Mbps, and IS in spec for XDCam, doesn't make sense to me to be doing ANY converting unless necessitated by a different spec.

Scott