cli.md

Using the command line

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The same engine that runs inside the GUI is also available as a command called smartcut. (If you installed the .deb, it is called smartcut-cli there — smartcut is the GUI.)

It is for repeating the same job, for calling from a script, and for machines with no screen to put a window on. It can do everything the GUI can.

Start with these six

smartcut input.ts --keep 5.3-12.7 -o out.ts   # keep only this range
smartcut input.ts --cut 8.0-20.0  -o out.ts   # drop this range
smartcut input.ts --analyze                   # just show what would happen

smartcut input.ts --analyze --detect-cm --logo  # list the commercial candidates
smartcut input.ts --analyze --scenes            # list the scene changes

smartcut input.ts --cut 8.0-20.0 --bdav ~/disc  # onto a disc instead of a file

• --keep and --cut can be given as many times as you like. --keep 0-60 --keep 180-240 keeps those two ranges.
• Times can be plain seconds or the 1:23:45.6 form.
• --analyze writes nothing. It prints the plan — what gets copied and what gets rebuilt. Running it first is the safe way to check before committing.

Choosing where to cut

Option	Meaning
--keep START-END	A range to keep. Repeatable
--cut START-END	A range to drop. Repeatable
--no-open-gop	Never start a copy at an open GOP
--clean-joins	Re-encode up to two extra seconds at the start of each range, far enough to reach a point where no picture comes out of the decoder in the wrong order. Off by default — see the note below

What --clean-joins costs. At an ordinary join, the pictures a copy makes are already exact; the only thing wrong is the order one of them comes out in. --clean-joins avoids that by rebuilding two seconds, and those two seconds stop being a copy of the recording (about 51 dB against the original). That trades something certain for something occasional, which is why it is off.

Choosing where the output goes

Option	Meaning
-o OUTPUT	Output path. The extension picks the container
--drop-stream INDEX	Leave one of the recording's streams out of the output. Repeatable. The same thing the cut editor's Tracks menu does
--title N	Which recording on a disc (a folder or an .iso) to open. Part of the programme's name works in place of the number. Left out, it lists what is on the disc and stops

Audio

By default the sound is treated like the video: only the few frames a join falls inside are rebuilt (smart rendering). Give any of the five settings below a value the recording does not already have and there is no frame left to copy, so the whole track is re-encoded.

Option	Meaning
--audio-mode smart|copy|reencode	smart is the default: it rebuilds only the frames a boundary falls inside, so nothing from the far side of a cut is heard — and nothing at all when the join falls in silence. copy is lossless to the byte but leaves a little of the far side audible; reencode cuts to the sample at the cost of rebuilding the whole track
--audio-codec source|aac|lpcm|ac3|dts	What the audio is written as. source, the default, keeps the recording's own. AAC plays straight off a phone, AC-3 and DTS are what an AV receiver handles most reliably, and linear PCM is uncompressed
--audio-channels N	Channel count, 1 to 8. Anything but the recording's own is a downmix — 5.1 folded to stereo, for instance
--audio-samplerate RATE	Sample rate, as 48k or 48000. Codecs differ in what they support (AC-3 has three rates, Blu-ray LPCM three others); a rate a codec does not have is taken to the nearest one it does, with a note saying which
--audio-bits 16|24	How wide each sample is. Only meaningful for linear PCM — the other codecs write a description of the sound rather than the sound itself, so there is nowhere to put a width
--audio-bitrate RATE	Bits per second when re-encoding, as 192k or 192000. Left out, it follows the recording. A figure the encoder will not accept is raised to what that codec is ordinarily carried at, with a note saying so
--aac auto|mpeg2|mpeg4	Which flavour of AAC the frames SmartCut writes announce themselves as. auto, the default, follows the recording — MPEG-2 AAC for a broadcast
--audio-es	Also write the sound out as a bare stream beside the output. AAC only
--audio-fade SECONDS	Take the level down into each seam and bring it back out over that many seconds. 0 to 10; 0, no fade, is the default

What --audio-fade reaches. Only sound this program writes: smart and reencode fade, copy does not, and neither does sound carried through whole because re-encoding it would lose what makes it lossless (TrueHD, DTS-HD MA). Where it cannot be applied the cut says so. The beginning and the end of the output are left alone: a fade is for a place where two pieces meet.

Writing a broadcast .ts

Option	Meaning
--tables partial|broadcast|muxer	How a transport stream describes its own contents. Unsaid, a .ts gets broadcast — the recording's own SDT, EIT and TOT, which is where a player reads the programme name, the station and the clock — and a .m2ts gets partial, the shape a disc's stream is written in. muxer adds nothing. --no-tables is the old name for muxer
--no-data-broadcast	Leave out the recording's data broadcast — what is behind the d button. It is otherwise carried into any .ts that keeps the broadcast's own tables, which is the only shape that can hold one: the modules come out whole and byte for byte, so a receiver draws the same pages. What turning it down buys is size — a carousel is between a hundredth and a fifth of what a broadcast multiplex spends. --data-broadcast asks for it outright, which only changes what is said when it cannot be carried

Writing a disc (BDAV)

--bdav writes the same shape a recorder writes to a BD-RE — a folder, not a file. The disc decides the filenames, so -o is not used. If a disc is already there, the recording is added to it.

Option	Meaning
--bdav FOLDER	Write a BDAV disc into this folder (one recording becomes BDAV/STREAM/00001.m2ts). The index is built afterwards
--fit bd25|bd50|bd100|bd128|BYTES	Write the pictures back smaller, by as much as it takes for the output to fit that much room. Where it already fits, nothing is done. The sound, the subtitles and the programme information are untouched; only the pictures give anything up. MPEG-2 only -- anything else is written at its full size and says so. What share they will be written at is printed before the writing starts. See Fitting a disc
--video-share 0.35..1	The share itself, where you would rather name it than have a size worked out into one
--iso 2.50|2.60	Wrap the finished disc in an .iso beside it: --bdav ~/disc writes ~/disc/BDAV and ~/disc.iso. The folder stays
--iso-access read-only|overwritable	What the image says may be done to the disc it is burned onto. read-only, the default, is the truth about a disc nothing will write to again — a BD-R, or a BD-RE you only play. overwritable is what a recorder writes on a BD-RE, and what it wants to see before it will add a recording to the disc or take one off. Needs --iso
--iso-only	And then take the folder away, leaving the image on its own. Needs --iso: the image is made of the folder, so the folder is written first and goes once the image holds it. What goes is BDAV, and the folder above it only where that leaves it empty — a disc written into a folder of your own leaves everything else in it alone
--disc-title NAME	What the disc is called. Left out, the series the recording is an episode of: the programme name with the episode number, the episode's own title and the broadcast's marks taken off it
--programme NAME	What this recording is called in the disc's index. Left out, the name its playlist gave it if it came off a disc, otherwise the programme name the broadcast carries
--channel NAME[,N]	The channel, and optionally the three digits a viewer knows it by (--channel "衛星第一,161"). Left out, both come from the recording
--about TEXT	What the disc's index says the programme was. Left out, the description the recording carries
--made "Y-M-D H:M:S"	When the recording was made. Left out, when the programme went out, where the recording still says

Looking before you write

Option	Meaning
--analyze	Work out the plan and print it. Writes nothing — not even into a --bdav folder
--detect-cm	Look for the commercial breaks
--logo	Let commercial detection use the station logo as well
--scenes	List the scene changes
--preview TIME	Decode one picture at TIME and write it as a JPEG (preview.jpg, or -o). It prints the time actually decoded beside the time asked for
--cut-near TIME	Print where the nearest picture-to-picture change is to TIME, in windows of ±0.5, ±1 and ±2 seconds

Index and proxy

Option	Meaning
--seek-index PATH	Where to keep the seek index. Written on the first run and read on the next, which saves walking the recording again
--index auto|disc|scan|container	Where the entry points come from. auto, the default, asks whoever already knows and falls back: the disc's own map, then the container's seek table, then the walk over the packets. disc and container ask one of those and stop; scan always walks, which is what a transport stream needs — it has neither table. A container table is taken only where it covers the whole recording
--proxy	Build the editing proxy (a light stand-in file) beside the recording and stop (.proxy.mp4, or -o)
--as-proxy	Treat the input as a proxy rather than a recording — how a proxy is checked against what it stands in for

A disc's subtitles

Option	Meaning
--subtitles pgs|beside|sup	Where the subtitles a disc draws go. pgs, the default, puts them inside the cut as the kind a transport stream carries — a Blu-ray's own untouched, a DVD's converted to it. beside writes them next to the cut as the .idx and .sub pair every player and subtitle tool reads — a DVD's own untouched, a Blu-ray's read back out of its display sets. sup writes those display sets themselves, into a .sup next to the cut — a Blu-ray's subtitles byte for byte, and what BDSup2Sub and Subtitle Edit read
--drop-subpicture ID	Leave one of a DVD's subtitle streams out, by the id the disc knows it by (0x20). Repeatable

Only a .ts or an .m2ts can hold subtitles inside it. Asked for an .mp4, SmartCut says so and writes the pair beside it instead — beside the cut is the one way a cut of a disc in that container keeps its subtitles. A .sup holds one stream, so a recording with two of them is written as two files, named by language (cut_title.eng.sup). See a disc's subtitles.

VC-1 discs

Option	Meaning
--vc1-quant 3..31	How finely the join pictures of VC-1 material are written; 3 is the finest. The default is 4, which lands around 46 dB against the pictures it replaces

This setting exists only for VC-1 because there is no VC-1 encoder anywhere — not in FFmpeg, not on a graphics card. SmartCut writes those join pictures itself, and this is how finely. The details are in the Rust core.