Struct StreamMap 

pub struct StreamMap { /* private fields */ }

Parameters for one stream mapping of an Output: an FFmpeg-style specifier plus optional per-map encoder selection.

This is the builder-API equivalent of the FFmpeg CLI’s indexed per-stream options. One -map plus its matching -c/-b/… options become one StreamMap:

-map "[v0]" -c:v:0 libx264 -b:v:0 4M -preset:v:0 slow
-map "[v1]" -c:v:1 libx265 -crf:v:1 22
-map 0:a:0  -c:a:0 aac     -b:a:0 128k
-map 0:a:1  -c:a:1 libopus -b:a:1 96k

use ez_ffmpeg::{Output, StreamMap};

let output = Output::from("out.mkv")
    .add_stream_map(StreamMap::new("[v0]").codec("libx264")
        .codec_opt("b", "4M").codec_opt("preset", "slow"))
    .add_stream_map(StreamMap::new("[v1]").codec("libx265")
        .codec_opt("crf", "22"))
    .add_stream_map(StreamMap::new("0:a:0").codec("aac").codec_opt("b", "128k"))
    .add_stream_map(StreamMap::new("0:a:1").codec("libopus").codec_opt("b", "96k"));

Precedence

• Encoder: per-map codec > per-type set_video_codec / set_audio_codec / set_subtitle_codec > the container format’s default encoder.
• Options: per-map codec_opt entries are merged key by key over the per-type set_video_codec_opt / set_audio_codec_opt tables — the FFmpeg semantics, where every option matches its stream specifier independently (-b:v 4M -preset:v:0 slow leaves stream v:0 with both the bitrate and the preset). A per-map key overrides the same-named per-type key; other per-type keys still apply.

This “more specific wins, per key” chain is the builder equivalent of the CLI’s “last matching option is applied” rule.

Map granularity is binding granularity

A map that expands to several streams applies its codec to all of them: StreamMap::new("0:a").codec("aac") re-encodes every audio stream of input 0 with AAC (like -c:a aac). To give two streams different encoders, write two single-stream maps ("0:a:0", "0:a:1"), exactly like splitting one coarse -map 0 into indexed maps on the CLI.

Copy

codec("copy") selects stream copy for the map, equivalent to Output::add_stream_map_with_copy (FFmpeg -c:<spec> copy). Combining copy with a different per-map codec, or with codec_opt entries, is rejected at build time with OpenOutputError::StreamMapCopyConflict: copied packets never pass through an encoder, so those settings could never take effect.

A negative (disabling) map such as "-0:v" only disables previously matched streams; attaching a codec or codec options to one is rejected at build time as well.

Implementations

impl StreamMap

pub fn new(spec: impl Into<String>) -> Self

Creates a mapping for spec, an FFmpeg-style stream specifier ("0:v", "1:a:0", "0:s?") or a filter output label ("[v0]").

Without further calls this is exactly Output::add_stream_map(spec).

pub fn codec(self, name: impl Into<String>) -> Self

Selects the encoder for every stream this map matches — the builder form of FFmpeg’s indexed -c:v:0 libx264.

"copy" selects stream copy (see the type-level docs). Calling codec again replaces the previous value.

pub fn codec_opt(self, key: impl Into<String>, value: impl Into<String>) -> Self

Adds one encoder option for every stream this map matches — the builder form of FFmpeg’s indexed -b:v:0 4M / -preset:v:0 slow.

Per-map entries override same-named per-type options key by key (see the type-level docs). Repeating a key keeps the last value.

Trait Implementations

impl Clone for StreamMap

fn clone(&self) -> StreamMap

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for StreamMap

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: Into<String>> From<T> for StreamMap

A plain specifier string is a map with no per-map overrides, so every pre-existing add_stream_map("0:v") call keeps compiling unchanged.

fn from(linklabel: T) -> Self

Converts to this type from the input type.