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/*
GoToSocial
Copyright (C) 2021-2023 GoToSocial Authors admin@gotosocial.org
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package media
import (
"fmt"
"io"
"os"
"github.com/abema/go-mp4"
)
type gtsVideo struct {
frame *gtsImage
duration float32 // in seconds
bitrate uint64
framerate float32
}
// decodeVideoFrame decodes and returns an image from a single frame in the given video stream.
// (note: currently this only returns a blank image resized to fit video dimensions).
func decodeVideoFrame(r io.Reader) (*gtsVideo, error) {
// We'll need a readseeker to decode the video. We can get a readseeker
// without burning too much mem by first copying the reader into a temp file.
// First create the file in the temporary directory...
tmp, err := os.CreateTemp(os.TempDir(), "gotosocial-")
if err != nil {
return nil, err
}
defer func() {
tmp.Close()
os.Remove(tmp.Name())
}()
// Now copy the entire reader we've been provided into the
// temporary file; we won't use the reader again after this.
if _, err := io.Copy(tmp, r); err != nil {
return nil, err
}
// probe the video file to extract useful metadata from it; for methodology, see:
// https://github.com/abema/go-mp4/blob/7d8e5a7c5e644e0394261b0cf72fef79ce246d31/mp4tool/probe/probe.go#L85-L154
info, err := mp4.Probe(tmp)
if err != nil {
return nil, fmt.Errorf("error probing tmp file %s: %w", tmp.Name(), err)
}
var (
width int
height int
video gtsVideo
)
for _, tr := range info.Tracks {
if tr.AVC == nil {
continue
}
if w := int(tr.AVC.Width); w > width {
width = w
}
if h := int(tr.AVC.Height); h > height {
height = h
}
if br := tr.Samples.GetBitrate(tr.Timescale); br > video.bitrate {
video.bitrate = br
} else if br := info.Segments.GetBitrate(tr.TrackID, tr.Timescale); br > video.bitrate {
video.bitrate = br
}
if d := float64(tr.Duration) / float64(tr.Timescale); d > float64(video.duration) {
video.framerate = float32(len(tr.Samples)) / float32(d)
video.duration = float32(d)
}
}
// Check for empty video metadata.
var empty []string
if width == 0 {
empty = append(empty, "width")
}
if height == 0 {
empty = append(empty, "height")
}
if video.duration == 0 {
empty = append(empty, "duration")
}
if video.framerate == 0 {
empty = append(empty, "framerate")
}
if video.bitrate == 0 {
empty = append(empty, "bitrate")
}
if len(empty) > 0 {
return nil, fmt.Errorf("error determining video metadata: %v", empty)
}
// Create new empty "frame" image.
// TODO: decode frame from video file.
video.frame = blankImage(width, height)
return &video, nil
}
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