FFMPEG: Guessed channel mono instead of stereo

[batko]

I am very new at FFMPEG and just started learning.

So I have an MXF file and I want to rewrap it to MOV, but do not touch audio and video settings. So the command I use is:

ffmpeg -i input_file.mxf -acodec copy -vcodec copy -f mov output_file.mov

However, even though audio in my input file is 2 channels stereo, FFMPEG gives me mono output. After the conversion, this information appears:

Guessed Channel Layout for Input Stream #0.1 : mono
Guessed Channel Layout for Input Stream #0.2 : mono

My question is, what command should I use to force FFMPEG guesses Channel Layout as stereo?

[JVRaines]

You can try putting -ac 2 before the -i option. If that doesn't work, you can try adding -map_channel 0.1.0 -map_channel 0.2.0 somewhere before the output filename. BTW, your -f option is optional because FFmpeg will know you want MOV format from the filename extension.

[raffriff42]

Your source has 2 audio streams, which need to be merged to create stereo.
amerge does the job, but it requires re-encoding the audio:

ffmpeg -y -hide_banner ^
-i "video+2audiostreams.mxf" ^
-filter_complex "[0:1:a][0:2:a]amerge" ^
-channel_layout stereo ^
-c:v copy -c:a aac -q:a 0.35 ^
"video+stereo.mxf"

Without re-encoding, it might be possible to flag the 2 streams as "L" and "R", but it won't be stereo.

[JVRaines]

Does it really have two streams or is FFmpeg misreading the file? OP tells us it is stereo. Perhaps a MediaInfo report would clarify.

[batko]

Thank you for advices. I exported it from Premiere with only one audio track, so I have no idea why it would possibly have two streams. Here is MediaFile report:

Format : MXF
Commercial name : XDCAM HD422
Format version : 1.2
Format profile : OP-1a
Format settings : Closed / Complete
File size : 49,3 MiB
Duration : 8s 40 ms
Overall bit rate : 51,4 Mb/s
Package name : Source Package
Encoded date : 2017-02-20 14:41:52.928
Writing application : Adobe Systems Incorporated Premiere Pro 1.0.0.0.1
Writing library : win32 4.5.13.0.3

Wideo
ID : 512
Format : MPEG Video
Commercial name : XDCAM HD422
Format version : Version 2
Format profile : 4:2:2@High
Format settings, BVOP : Tak
Format settings, Matrix : Własny
Format settings, GOP : Variable
Format settings, picture structure : Frame
Format settings, wrapping mode : Frame
Codec ID : 0D01030102046001-0401020201040300
Duration : 8s 40 ms
Bit rate mode : Stała
Bit rate : 50,0 Mb/s
Width : 1.920 pikseli
Height : 1.080 pikseli
Display aspect ratio : 16:9
Frame rate : 25,000 kl/s
Standard : Component
Color space : YUV
Chroma subsampling : 4:2:2
Bit depth : 8 bitów
Scan type : Z przeplotem
Scan order : Górne pole wpierw
Bits/(Pixel*Frame) : 0.965
Time code of first frame : 00:00:00:00
Time code source : Group of pictures header
Stream size : 47,9 MiB (97%)
Color primaries : BT.709
Transfer characteristics : BT.709

Audio #1
ID : 768
Format : PCM
Format settings, Endianness : Little
Format settings, wrapping mode : Frame (AES)
Codec ID : 0D01030102060300
Duration : 8s 40 ms
Bit rate mode : Stała
Bit rate : 768 kb/s
Channel(s) : 1 kanał
Sampling rate : 48,0 kHz
Frame rate : 25,000 kl/s (1920 spf)
Bit depth : 16 bitów
Stream size : 754 KiB (1%)
Locked : Yes

Audio #2
ID : 1024
Format : PCM
Format settings, Endianness : Little
Format settings, wrapping mode : Frame (AES)
Codec ID : 0D01030102060300
Duration : 8s 40 ms
Bit rate mode : Stała
Bit rate : 768 kb/s
Channel(s) : 1 kanał
Sampling rate : 48,0 kHz
Frame rate : 25,000 kl/s (1920 spf)
Bit depth : 16 bitów
Stream size : 754 KiB (1%)
Locked : Yes

Other #1
ID : 0-Material
Type : Time code
Format : MXF TC
Time code of first frame : 00:00:00:00
Time code settings : Material Package
Time code, striped : Tak

Other #2
ID : 0-Source
Type : Time code
Format : MXF TC
Time code of first frame : 00:00:00:00
Time code settings : Source Package
Time code, striped : Tak

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

[Marsia Mariner]

The truth is, MXF is a weird & stupid container. Different from the good ones, it uses ONE audio channel per stream. Compared to the other containers, it does not know the meaning of «multichannel audio».