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Fix small segments cut at beginning of transcode blocks

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Zoe Roux 2024-04-03 23:42:46 +02:00
parent 3abdb0a4c4
commit 7c9bb11d14
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1 changed files with 26 additions and 14 deletions
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40
transcoder/src/stream.go
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@ -160,25 +160,32 @@ func (ts *Stream) run(start int32) error {
start_ref := float64(0)
start_segment := start
if start != 0 {
// we always take on segment before the current one, for different reasons for audio/video:
// - Audio: we need context before the starting point, without that ffmpeg doesnt know what to do and leave ~100ms of silence
// - Video: if a segment is really short (between 20 and 100ms), the padding given in the else block bellow is not enough and
// the previous segment is played another time. the -segment_times is way more precise so it does not do the same with this one
start_segment = start - 1
if ts.handle.getFlags()&AudioF != 0 {
// when segmenting audio, we need -ss to have the context before the start time
// without it, the cut loses a bit of audio (audio gap of ~100ms)
start_segment = start - 1
}
// the param for the -ss takes the keyframe before the specificed time
// (if the specified time is a keyframe, it either takes that keyframe or the one before)
// to prevent this weird behavior, we specify a bit after the keyframe that interest us
if start_segment+1 == length {
start_ref = (ts.file.Keyframes.Get(start_segment) + float64(ts.file.Info.Duration)) / 2
start_ref = ts.file.Keyframes.Get(start_segment)
} else {
start_ref = (ts.file.Keyframes.Get(start_segment) + ts.file.Keyframes.Get(start_segment+1)) / 2
// the param for the -ss takes the keyframe before the specificed time
// (if the specified time is a keyframe, it either takes that keyframe or the one before)
// to prevent this weird behavior, we specify a bit after the keyframe that interest us
// this can't be used with audio since we need to have context before the start-time
// without this context, the cut loses a bit of audio (audio gap of ~100ms)
if start_segment+1 == length {
start_ref = (ts.file.Keyframes.Get(start_segment) + float64(ts.file.Info.Duration)) / 2
} else {
start_ref = (ts.file.Keyframes.Get(start_segment) + ts.file.Keyframes.Get(start_segment+1)) / 2
}
}
}
end_padding := int32(1)
if end == length {
end_padding = 0
}
segments := ts.file.Keyframes.Slice(start+1, end+end_padding)
segments := ts.file.Keyframes.Slice(start_segment+1, end+end_padding)
if len(segments) == 0 {
// we can't leave that empty else ffmpeg errors out.
segments = []float64{9999999}
@ -194,7 +201,9 @@ func (ts *Stream) run(start int32) error {
"-nostats", "-hide_banner", "-loglevel", "warning",
}
args = append(args, Settings.HwAccel.DecodeFlags...)
if ts.handle.getFlags()&VideoF != 0 {
args = append(args, Settings.HwAccel.DecodeFlags...)
}
if start_ref != 0 {
if ts.handle.getFlags()&VideoF != 0 {
@ -237,7 +246,10 @@ func (ts *Stream) run(start int32) error {
args = append(args,
"-f", "segment",
// needed for rounding issues when forcing keyframes
"-segment_time_delta", "0.2",
// recommanded value is 1/(2*frame_rate), which for a 24fps is ~0.021
// we take a little bit more than that to be extra safe but too much can be harmfull
// when segments are short (can make the video repeat itself)
"-segment_time_delta", "0.05",
"-segment_format", "mpegts",
"-segment_times", toSegmentStr(Map(segments, func(seg float64, _ int) float64 {
// segment_times want durations, not timestamps so we must substract the -ss param
@ -247,7 +259,7 @@ func (ts *Stream) run(start int32) error {
})),
"-segment_list_type", "flat",
"-segment_list", "pipe:1",
"-segment_start_number", fmt.Sprint(start),
"-segment_start_number", fmt.Sprint(start_segment),
outpath,
)