Change rotation flag in MP4 video (without losing metadata)

by aXeL-HH   Last Updated March 28, 2018 13:01 PM

I just want to change the rotation flag in a .mp4 video file. Many similar questions exist, most answers suggest using

ffmpeg -i input.mp4 -map_metadata 0 -metadata:s:v rotate=90 -codec copy output.mp4

My problem with those solutions is that even though it copies most of the metadata, some parts are lost, and the file is 700kb smaller. Attached is before and after metadata from ffprobe and exifer.

An additional odd finding is the ffmpeg rotate=90 command makes a ccw rotation, which in ffprobe is (cw) 270° in metadata, but (ccw)90° in displaymatrix side data.

= equal attributes
* altered attributes
- removed attributes
+ added attributes

ffprobe input.mp4

*Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '.\input.mp4':
=  Metadata:
*    major_brand     : avc1
*    minor_version   : 0
*    compatible_brands: avc1isom
=    creation_time   : 2016-10-29T12:10:41.000000Z
-    firmware        : HD3.11.03.03
*  Duration: 00:00:06.01, start: 0.000000, bitrate: 32072 kb/s
=    Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, bt709), 1920x1440 [SAR 1:1 DAR 4:3], 30945 kb/s, 47.95 fps, 47.95 tbr, 720k tbn, 95.90 tbc (default)
=    Metadata:
=      creation_time   : 2016-10-29T12:10:41.000000Z
*      handler_name    :  GoPro AVC
-      encoder         : GoPro AVC encoder
-    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 127 kb/s (default)
-    Metadata:
-      creation_time   : 2016-10-29T12:10:41.000000Z
-      handler_name    :  GoPro AAC

ffprobe output.mp4

*Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '.\output.mp4':
=  Metadata:
*    major_brand     : isom
*    minor_version   : 512
*    compatible_brands: isomiso2avc1mp41
=    creation_time   : 2016-10-29T12:10:41.000000Z
+    encoder         : Lavf58.10.100
*  Duration: 00:00:06.01, start: 0.000000, bitrate: 30948 kb/s
=    Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, bt709), 1920x1440 [SAR 1:1 DAR 4:3], 30945 kb/s, 47.95 fps, 47.95 tbr, 720k tbn, 95.90 tbc (default)
=    Metadata:
+      rotate          : 270
=      creation_time   : 2016-10-29T12:10:41.000000Z
*      handler_name    : VideoHandler
+    Side data:
+      displaymatrix: rotation of 90.00 degrees

exiftool input.mp4

=ExifTool Version Number         : 10.87
*File Name                       : input.mp4
=Directory                       : C:/
*File Size                       : 23 MB
*File Modification Date/Time     : 2016:10:29 13:10:48+02:00
*File Access Date/Time           : 2018:03:22 22:51:11+01:00
*File Creation Date/Time         : 2018:03:22 22:51:11+01:00
=File Permissions                : rw-rw-rw-
=File Type                       : MP4
=File Type Extension             : mp4
=MIME Type                       : video/mp4
*Major Brand                     : MP4 Base w/ AVC ext [ISO 14496-12:2005]
*Minor Version                   : 0.0.0
*Compatible Brands               : avc1, isom
=Movie Header Version            : 0
=Create Date                     : 2016:10:29 12:10:41
=Modify Date                     : 2016:10:29 12:10:41
*Time Scale                      : 90000
=Duration                        : 6.01 s
=Preferred Rate                  : 1
=Preferred Volume                : 100.00%
=Preview Time                    : 0 s
=Preview Duration                : 0 s
=Poster Time                     : 0 s
=Selection Time                  : 0 s
=Selection Duration              : 0 s
=Current Time                    : 0 s
*Next Track ID                   : 3
-Firmware Version                : HD3.11.03.03
-Lens Serial Number              : LW13121003000141
-Camera Serial Number Hash       : 4833422b363033313530636432356400
=Track Header Version            : 0
=Track Create Date               : 2016:10:29 12:10:41
=Track Modify Date               : 2016:10:29 12:10:41
=Track ID                        : 1
=Track Duration                  : 6.01 s
=Track Layer                     : 0
=Track Volume                    : 0.00%
=Image Width                     : 1920
=Image Height                    : 1440
=Graphics Mode                   : srcCopy
=Op Color                        : 0 0 0
=Compressor ID                   : avc1
=Source Image Width              : 1920
=Source Image Height             : 1440
=X Resolution                    : 72
=Y Resolution                    : 72
-Compressor Name                 : .GoPro AVC encoder
=Bit Depth                       : 24
-Color Representation            : nclc 1 1 1
-Gamma                           : 2.2
=Video Frame Rate                : 47.952
-Matrix Structure                : 1 0 0 0 1 0 0 0 1
=Media Header Version            : 0
=Media Create Date               : 2016:10:29 12:10:41
=Media Modify Date               : 2016:10:29 12:10:41
-Media Time Scale                : 48000
-Media Duration                  : 5.99 s
*Handler Type                    : Audio Track
-Handler Description             : .GoPro AAC
-Balance                         : 0
-Audio Format                    : mp4a
-Audio Channels                  : 2
-Audio Bits Per Sample           : 16
-Audio Sample Rate               : 48000
-Movie Data Size                 : 24045320
-Movie Data Offset               : 32768
*Avg Bitrate                     : 32 Mbps
=Image Size                      : 1920x1440
=Megapixels                      : 2.8
*Rotation                        : 0

exiftool output.mp4

=ExifTool Version Number         : 10.87
*File Name                       : output.mp4
=Directory                       : C:/
*File Size                       : 22 MB
*File Modification Date/Time     : 2018:03:23 12:29:19+01:00
*File Access Date/Time           : 2018:03:23 12:28:18+01:00
*File Creation Date/Time         : 2018:03:23 12:28:18+01:00
=File Permissions                : rw-rw-rw-
=File Type                       : MP4
=File Type Extension             : mp4
=MIME Type                       : video/mp4
*Major Brand                     : MP4  Base Media v1 [IS0 14496-12:2003]
*Minor Version                   : 0.2.0
*Compatible Brands               : isom, iso2, avc1, mp41
+Movie Data Size                 : 23232544
+Movie Data Offset               : 48
=Movie Header Version            : 0
=Create Date                     : 2016:10:29 12:10:41
=Modify Date                     : 2016:10:29 12:10:41
*Time Scale                      : 1000
=Duration                        : 6.01 s
=Preferred Rate                  : 1
=Preferred Volume                : 100.00%
=Preview Time                    : 0 s
=Preview Duration                : 0 s
=Poster Time                     : 0 s
=Selection Time                  : 0 s
=Selection Duration              : 0 s
=Current Time                    : 0 s
*Next Track ID                   : 2
=Track Header Version            : 0
=Track Create Date               : 2016:10:29 12:10:41
=Track Modify Date               : 2016:10:29 12:10:41
=Track ID                        : 1
=Track Duration                  : 6.01 s
=Track Layer                     : 0
=Track Volume                    : 0.00%
+Matrix Structure                : 0 1 0 -1 0 0 0 0 1
=Image Width                     : 1920
=Image Height                    : 1440
=Media Header Version            : 0
=Media Create Date               : 2016:10:29 12:10:41
=Media Modify Date               : 2016:10:29 12:10:41
+Media Time Scale                : 720000
+Media Duration                  : 6.01 s
+Media Language Code             : eng
+Handler Description             : VideoHandler
=Graphics Mode                   : srcCopy
=Op Color                        : 0 0 0
=Compressor ID                   : avc1
=Source Image Width              : 1920
=Source Image Height             : 1440
=X Resolution                    : 72
=Y Resolution                    : 72
=Bit Depth                       : 24
+Pixel Aspect Ratio              : 1:1
=Video Frame Rate                : 47.952
*Handler Type                    : Metadata
+Handler Vendor ID               : Apple
+Encoder                         : Lavf58.10.100
*Avg Bitrate                     : 30.9 Mbps
=Image Size                      : 1920x1440
=Megapixels                      : 2.8
*Rotation                        : 270

I compared ffmpeg rotate=0 and rotate=90 .mp4 files in notepad++ to identify the rotate flag / matrix, but without luck, just jibberish. I would prefer to just edit the flag (like exiftool is doing it for all kinds of metadata, but can't do rotate in videos) instead of streaming the content into a new container, also for faster processing (all videos are on NAS).



Answers 1


FFmpeg and similar programs change the metadata even with the -map_metadata option. exiftool can read the rotation matrix and rotation flag, but cannot write it.

To get true lossless (incl. metadata) rotation, I couldn't find a solution, so I grabbed a hex editor (eg HxD) and analyzed the rotated video files.

True lossless rotation of MP4:

  • open mp4 with hex editor and search for vide to find the metadata of the video track
  • some rows above (for my files mostly 9, sometimes 12) you should see trak...\tkhd
  • in between there should be an @ sign (HEX 40)
  • in the two rows before it the rotation matrix is stored
  • no rotation:

    00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
    00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    40
    
  • 180°:

    FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
    FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    40
    
  • 90° cw:

    00 00 00 00 00 01 00 00 00 00 00 00 FF FF 00 00 
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
    40 
    
  • 90° ccw:

    00 00 00 00 FF FF 00 00 00 00 00 00 00 01 00 00 
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
    40
    

Alter the file as you need it, and it should be rotated in players that support the rotation flag (most current players do).

In case your video contains stereo audio, this is obviously not switched, so in case you want the sound to match with video rotation (180°), you need to switch the left and right channels.

aXeL-HH
aXeL-HH
March 23, 2018 15:11 PM

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