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Make video start time detection smarter

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This commit is contained in:
Zoe Roux 2024-02-23 15:26:36 +00:00
parent 43350ee1fd
commit d71cd625d0
1 changed files with 9 additions and 33 deletions
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42
transcoder/src/filestream.go
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@ -55,35 +55,7 @@ func NewFileStream(path string, sha string, route string) *FileStream {
return ret
}
// sometimes, videos can start at a timing greater than 0:00. We need to take that into account
// and only list keyframes that come after the start of the video (without that, our segments count
// mismatch and we can have the same segment twice on the stream).
func GetStartTime(path string) (float64, error) {
// we can't run this ffprobe in the same call as below because stream entries
// are always after packet entries and we want to start processing packets as
// soon as possible (but we need start_time for that)
cmd := exec.Command(
"ffprobe",
"-loglevel", "quiet",
"-select_streams", "v:0",
"-show_entries", "stream=start_time",
"-of", "csv=p=0",
path,
)
out, err := cmd.Output()
if err != nil {
return 0, err
}
ret := strings.TrimSpace(string(out))
return strconv.ParseFloat(ret, 64)
}
func GetKeyframes(path string) ([]float64, bool, error) {
start_time, err := GetStartTime(path)
if err != nil {
return nil, false, err
}
defer printExecTime("ffprobe analysis for %s", path)()
// run ffprobe to return all IFrames, IFrames are points where we can split the video in segments.
// We ask ffprobe to return the time of each frame and it's flags
@ -108,8 +80,7 @@ func GetKeyframes(path string) ([]float64, bool, error) {
scanner := bufio.NewScanner(stdout)
ret := make([]float64, 1, 1000)
ret[0] = 0
ret := make([]float64, 0, 1000)
last := 0.
can_transmux := true
for scanner.Scan() {
@ -136,9 +107,14 @@ func GetKeyframes(path string) ([]float64, bool, error) {
// the segment time and decide to cut at a random keyframe. Having every keyframe
// handled as a segment prevents that.
if fpts <= start_time {
// look GetStartTime comment for explanations
// tldr: start time can be greater than 0, ignore keyframes before start_time
if len(ret) == 0 {
// sometimes, videos can start at a timing greater than 0:00. We need to take that into account
// and only list keyframes that come after the start of the video (without that, our segments count
// mismatch and we can have the same segment twice on the stream).
// we hardcode 0 as the first keyframe (even if this is fake) because it makes the code way easier to follow.
// this value is actually never sent to ffmpeg anyways.
ret = append(ret, 0)
continue
}