Rotation metadata on input video is ignored

[ivystopia]

Description:

When converting a video with embedded rotation metadata (e.g. a 1920×1080 video rotated 90° to be vertical), gifski ignores the metadata, so the GIF comes out rotated.

VLC and other players show the video correctly (as if it were actually 1080×1920).

Suggestions:

• Make gifski honour the rotation metadata
• Or add a command-line flag (e.g. --rotate=90)

Steps to Reproduce:

1. Use a video with rotation metadata.

   For example, a video whose mediainfo includes rotation data similar to:

   <track type="Video">
     ...
     <Rotation>90.000</Rotation>
     <Rotation_String>90°</Rotation_String>
     ...
   </track>

2. Run:

   gifski -o output.gif input.mp4

Workarounds:

Workaround 1: Pre-process the input video with FFmpeg:

ffmpeg -noautorotate -i input.mp4 -vf "transpose=1" -metadata:s:v:0 rotate=0 -c:v libx264 -qp 0 -c:a copy rotated.mp4
gifski -o output.gif rotated.mp4

Workaround 2: Extract PNG frames from the input video, rotate them, and use gifski on the frames:

# Extract frames to PNG files:
ffmpeg -i input.mp4 frame%04d.png

# Rotate PNGs 90° clockwise using ImageMagick:
mogrify -rotate 90 frame*.png

# Convert rotated PNGs to a GIF:
gifski -o output.gif frame*.png

Environment:

• OS: Ubuntu 24.04
• gifski: 1.32.0
• ffmpeg: 6.1.1-3ubuntu5
• ImageMagick: 6.9.12-98 Q16 x86_64 18038
• VLC: 4.0.0-dev (nightly)

[kornelski]

Do you know how to get that info from the ffmpeg API?

[Mr-Z-2697]

A better workaround is to use Y4M pipe, and transpose is only "half rotation", you then need to flip the video to get real rotation effect.

[zouzg7829]

the rotataion info can be get from the metadata of AVStream, for example:

int getRotateAngle(AVStream* avStream) {
    AVDictionaryEntry *tag = NULL;
    int   m_Rotate=-1;
    tag = av_dict_get(avStream->metadata, "rotate", tag, 0);
    if (tag==NULL) {
        m_Rotate = 0;
    } else {
        int angle = atoi(tag->value);
        angle %= 360;
        if (angle == 90) {
            m_Rotate = MT_VIDEO_ROTATE_90;
        } else if (angle == 180) {
            m_Rotate = MT_VIDEO_ROTATE_180;
        } else if (angle == 270) {
            m_Rotate = MT_VIDEO_ROTATE_270;
        } else {
            m_Rotate = MT_VIDEO_ROTATE_0;
        }
    }
    return m_Rotate;
}

btw, video have several metadatas

[zouzg7829]

ffprobe can get the rotation info:

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    creation_time   : 2023-01-07T03:46:36.000000Z
    com.android.version: 10
  Duration: 00:00:21.87, start: 0.000000, bitrate: 20360 kb/s
    Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, bt470bg/bt470bg/smpte170m), 1920x1080, 19968 kb/s, SAR 1:1 DAR 16:9, 29.90 fps, 30 tbr, 90k tbn, 180k tbc (default)
    Metadata:
      rotate          : 90
      creation_time   : 2023-01-07T03:46:36.000000Z
      handler_name    : VideoHandle
    Side data:
      displaymatrix: rotation of -90.00 degrees
    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 96 kb/s (default)
    Metadata:
      creation_time   : 2023-01-07T03:46:36.000000Z
      handler_name    : SoundHandle

the output line "rotate : 90" show the info we need.