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fix(stream): delay_moov en el remux para audio AAC con dts negativo

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El remux reencodea el audio no-AAC (eac3→aac); la pista AAC arranca con un
dts negativo (priming/encoder-delay). Con empty_moov el moov se escribía
ANTES de conocer ese delay, así que el primer fragmento quedaba mal formado
y un demuxer estricto (Safari / la forma en que Apple decodifica HEVC) nunca
inicializaba la reproducción: el <video> cargaba bytes (se veía en Network)
pero no arrancaba, y el player re-bootstrapeaba la sesión cada pocos segundos.

Añade +delay_moov: retiene el moov hasta el primer paquete y maneja el dts
de priming. ffmpeg deja de emitir el warning "nonzero dts ... moov already
written" y el fMP4 reproduce. Reproducido con Hoppers (HEVC Main 10 + EAC3).
This commit is contained in:
Deivid Soto 2026-06-10 20:10:11 +02:00
parent b0637f266b
commit 671bee8317
1 changed files with 9 additions and 1 deletions
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10
internal/engine/transcoder.go
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@ -302,8 +302,16 @@ func buildFFmpegArgs(filePath string, opts TranscodeOpts) []string {
// until the whole mdat lands and playback never starts.
// * negative_cts_offsets: lets b-frames carry the right pts/dts so
// decoders don't reset the playhead to 0 every fragment.
// * delay_moov: a re-encoded AAC track starts with a negative dts (the
// encoder priming/delay). With empty_moov the moov is written up front,
// BEFORE that delay is known, so the first fragment is malformed and a
// strict demuxer (Safari, and any browser the way Apple decodes HEVC)
// never initialises playback — the <video> loads bytes but never starts,
// and the player re-bootstraps the session every few seconds. delay_moov
// holds the moov until the first packet so the priming dts is handled.
// (Was the "remux loads in Network but won't play" bug.)
args = append(args,
"-movflags", "+frag_keyframe+empty_moov+default_base_moof+negative_cts_offsets",
"-movflags", "+frag_keyframe+empty_moov+default_base_moof+negative_cts_offsets+delay_moov",
"-frag_duration", "1000000",
"-f", "mp4",
"pipe:1",