feat(streams): allow selecting video probe stream

Add --video-stream and [encoding].video_stream so users can choose which
input video stream is probed for preset helper variables.

Use the selected stream for codec, pixel format, frame rate, output
pixel format, and GOP size metadata while leaving preset stream mapping
unchanged.

Validate CLI stream selectors strictly and ignore invalid config values
with a warning so bad configuration falls back to the default v:0
stream.

Document the new option in the README and man page, add verbose dry-run
output, and provide bash completion for common video stream selectors.

Closes #6.

4 files changed, 194 insertions, 45 deletions

diff --git a/README.md b/README.md
index 720e0d5..c937595 100644
--- a/README.md
+++ b/README.md
@@ -30,6 +30,8 @@ replaces the original atomically on success.
 - **Size report** (`-s`) — print per-file size feedback, show a batch
   summary, and write a status TSV log for encoded, skipped, and failed files.
 - **Dry-run** (`-n`) — preview what would happen without touching any files.
+- **Selectable video probe stream** (`--video-stream`) — choose which input
+  video stream is probed for preset helper variables.
 - **Backup original** (`--backup-dir DIR`) — copy originals to an existing
   backup directory before replacing them.
 - **Nice** — runs ffmpeg at niceness 19 by default to avoid starving other
@@ -82,8 +84,10 @@ Presets live in:
 ${XDG_CONFIG_HOME:-$HOME/.config}/transcode.sh/presets/<name>.sh
 ```
 
-Each preset is sourced as Bash and must define an array named `ffargs`.
-The following variables are available to presets at source time:
+Each preset is sourced as Bash and must define an array named `ffargs`. The
+following variables are available to presets at source time. They are derived
+from the selected video probe stream, which defaults to `v:0` and can be
+changed with `--video-stream` or `[encoding] video_stream`:
 
 | Variable | Description |
 |----------|-------------|
@@ -104,6 +108,12 @@ these base arguments to `ffmpeg`:
 -c copy         # default to stream copy for every stream
 ```
 
+`--video-stream` only controls which input stream is probed for helper
+variables such as `input_codec`, `input_pixel_format`, `input_frame_rate`,
+`input_fps`, `output_pixel_format`, and `output_gop_size`. It does not rewrite
+the preset's `ffargs`; presets remain responsible for selecting which ffmpeg
+stream to encode.
+
 A preset therefore only needs to specify the streams it wishes to
 re-encode (typically `-c:v:0`) and any associated encoder options.
 All other streams — audio, subtitles, attachments — are passed through
@@ -156,6 +166,7 @@ Requires `tomlq` when the file is present.
 preset     = "av1"
 nice       = 10
 backup_dir = "backups"
+video_stream = "v:0"
 
 [skip]
 codecs = ["av1", "hevc"]
@@ -176,6 +187,7 @@ quiet   = false
 | `[encoding]` | `nice` | integer | `-N` |
 | `[encoding]` | `preset` | string | `-p` |
 | `[encoding]` | `verify_output` | boolean | `--verify-output` |
+| `[encoding]` | `video_stream` | string | `--video-stream` |
 | `[output]` | `quiet` | boolean | `-q` |
 | `[output]` | `verbose` | boolean | `-v` |
 | `[output]` | `ffmpeg_loglevel` | string | `--ffmpeg-loglevel` |
@@ -195,6 +207,12 @@ quiet   = false
 > **Note:** `[encoding] backup_dir` must point to an existing directory. CLI
 > `--backup-dir` always takes precedence.
 
+> **Note:** `[encoding] video_stream` selects the input video stream that is
+> probed for preset helper variables. It defaults to `"v:0"`. Invalid config
+> values are ignored with a warning and the default is used. CLI
+> `--video-stream` always takes precedence. This setting does not change ffmpeg
+> stream mapping in presets.
+
 ### Codec skip list (deprecated)
 
 The legacy `skip.conf` file is no longer read. If it still exists, a
@@ -228,6 +246,7 @@ transcode.sh [OPTION] [--] FILE...
 | `-l`, `--only-if-smaller` | Only replace original if new file is smaller |
 | `--no-only-if-smaller` | Do replace original even if new file is bigger |
 | `-p NAME`, `--preset NAME`, `--preset=NAME` | Preset to use (default: `default`) |
+| `--video-stream STREAM_SELECTOR`, `--video-stream=STREAM_SELECTOR` | Select the input video stream to probe for preset helper variables, e.g. `v:0` or `v:1` (default: `v:0`) |
 | `--ffmpeg-loglevel LEVEL`, `--ffmpeg-loglevel=LEVEL` | Specify the loglevel to pass to ffmpeg (default: `fatal`) |
 | `-q`, `--quiet` | Suppress all output (overrides `-v`) |
 | `-v`, `--verbose` | More detailed output |
@@ -262,6 +281,9 @@ transcode.sh --nice 10 --continue *.mp4
 
 # Load an alternative config file
 transcode.sh --config-file ~/profiles/fast.toml input.mp4
+
+# Probe the second video stream for preset helper variables
+transcode.sh --video-stream v:1 --dry-run --verbose input.mkv
 ```
 
 When `--backup-dir` is used, the directory must already exist. Backups preserve
diff --git a/transcode.sh b/transcode.sh
index 7f40e3b..817d8e2 100755
--- a/transcode.sh
+++ b/transcode.sh
@@ -164,6 +164,7 @@ PRESET_NAME="default"
 SIZE_REPORT=0
 SIZE_REPORT_FILE="transcode_size_report"
 VERIFY_OUTPUT=1
+VIDEO_STREAM="v:0"
 declare -A SKIP_CODECS
 
 REMAINING_ARGS=()
@@ -192,6 +193,7 @@ _CLI_SKIP_CODECS=()
 _CLI_SKIP_CODECS_OVERRIDE=0
 _CLI_VERBOSE=0
 _CLI_VERIFY_OUTPUT=0
+_CLI_VIDEO_STREAM=0
 
 # Values for size report
 _REPORT_ENCODING_FAILED=0
@@ -284,44 +286,45 @@ ${BOLD}${BLUE}Usage:${ALL_OFF} ${BOLD}${MAGENTA}%s${ALL_OFF} ${BOLD}${YELLOW}[OP
 Long options that take a value also accept ${BOLD}${YELLOW}--option${ALL_OFF}${BOLD}${CYAN}=${ALL_OFF}${BOLD}${GREEN}VALUE${ALL_OFF} syntax.
 
 ${BOLD}${BLUE}Encoding options:${ALL_OFF}
-  ${BOLD}${YELLOW}-p, --preset${ALL_OFF} ${BOLD}${GREEN}NAME${ALL_OFF}             load ffmpeg arguments from a preset (default: ${BOLD}${RED}%s${ALL_OFF})
-  ${BOLD}${YELLOW}-N, --nice${ALL_OFF} ${BOLD}${GREEN}VALUE${ALL_OFF}              nice adjustment for ffmpeg (default: ${BOLD}${RED}%d${ALL_OFF})
-  ${BOLD}${YELLOW}-n, --dry-run${ALL_OFF}                 show what would be done, do not run ffmpeg
-  ${BOLD}${YELLOW}    --backup-dir${ALL_OFF} ${BOLD}${GREEN}DIR${ALL_OFF}          backup original files to DIR instead of overwriting them
-  ${BOLD}${YELLOW}    --hwaccel${ALL_OFF} ${BOLD}${GREEN}[METHOD]${ALL_OFF}        enable hardware acceleration; METHOD defaults to ${BOLD}${RED}auto${ALL_OFF}
-                                if omitted
-  ${BOLD}${YELLOW}    --no-hwaccel${ALL_OFF}              disable hardware acceleration (do not pass ${BOLD}${YELLOW}-hwaccel${ALL_OFF} to ffmpeg)
-  ${BOLD}${YELLOW}-l, --only-if-smaller${ALL_OFF}         only replace original if new file is smaller
-      ${BOLD}${YELLOW}--no-only-if-smaller${ALL_OFF}      do replace original even if new file is bigger
-  ${BOLD}${YELLOW}-c, --continue${ALL_OFF}                continue with the next file even if ffmpeg fails
-      ${BOLD}${YELLOW}--no-continue${ALL_OFF}             do not continue with the next file if ffmpeg fails
-      ${BOLD}${YELLOW}--verify-output${ALL_OFF}           probe output with ffprobe before replacing original (default)
-      ${BOLD}${YELLOW}--no-verify-output${ALL_OFF}        skip the post-encode integrity check
+  ${BOLD}${YELLOW}-p, --preset${ALL_OFF} ${BOLD}${GREEN}NAME${ALL_OFF}                   load ffmpeg arguments from a preset (default: ${BOLD}${RED}%s${ALL_OFF})
+  ${BOLD}${YELLOW}-N, --nice${ALL_OFF} ${BOLD}${GREEN}VALUE${ALL_OFF}                    nice adjustment for ffmpeg (default: ${BOLD}${RED}%d${ALL_OFF})
+  ${BOLD}${YELLOW}-n, --dry-run${ALL_OFF}                       show what would be done, do not run ffmpeg
+  ${BOLD}${YELLOW}    --backup-dir${ALL_OFF} ${BOLD}${GREEN}DIR${ALL_OFF}                backup original files to DIR instead of overwriting them
+      ${BOLD}${YELLOW}--hwaccel${ALL_OFF} ${BOLD}${GREEN}[METHOD]${ALL_OFF}              enable hardware acceleration; METHOD defaults to ${BOLD}${RED}auto${ALL_OFF}
+                                      if omitted
+      ${BOLD}${YELLOW}--video-stream${ALL_OFF} ${BOLD}${GREEN}STREAM_SELECTOR${ALL_OFF}  video stream to probe for preset helper variables (default: ${BOLD}${RED}v:0${ALL_OFF})
+  ${BOLD}${YELLOW}    --no-hwaccel${ALL_OFF}                    disable hardware acceleration (do not pass ${BOLD}${YELLOW}-hwaccel${ALL_OFF} to ffmpeg)
+  ${BOLD}${YELLOW}-l, --only-if-smaller${ALL_OFF}               only replace original if new file is smaller
+      ${BOLD}${YELLOW}--no-only-if-smaller${ALL_OFF}            do replace original even if new file is bigger
+  ${BOLD}${YELLOW}-c, --continue${ALL_OFF}                      continue with the next file even if ffmpeg fails
+      ${BOLD}${YELLOW}--no-continue${ALL_OFF}                   do not continue with the next file if ffmpeg fails
+      ${BOLD}${YELLOW}--verify-output${ALL_OFF}                 probe output with ffprobe before replacing original (default)
+      ${BOLD}${YELLOW}--no-verify-output${ALL_OFF}              skip the post-encode integrity check
 
 ${BOLD}${BLUE}Input options:${ALL_OFF}
-      ${BOLD}${YELLOW}--config-file${ALL_OFF} ${BOLD}${GREEN}FILE${ALL_OFF}        load configuration from FILE instead of the default path
-  ${BOLD}${YELLOW}-f, --encode-file${ALL_OFF} ${BOLD}${GREEN}FILE${ALL_OFF}        file containing a list of files to encode
-  ${BOLD}${YELLOW}-S, --skip-codec${ALL_OFF} ${BOLD}${GREEN}LIST${ALL_OFF}         skip files with these codecs;
-                                ${BOLD}${GREEN}LIST${ALL_OFF} is comma, space, or colon separated
-      ${BOLD}${YELLOW}--skip-codec-override${ALL_OFF}     use only codecs from --skip-codec,
-                                ignoring [skip].codecs from config
+      ${BOLD}${YELLOW}--config-file${ALL_OFF} ${BOLD}${GREEN}FILE${ALL_OFF}              load configuration from FILE instead of the default path
+  ${BOLD}${YELLOW}-f, --encode-file${ALL_OFF} ${BOLD}${GREEN}FILE${ALL_OFF}              file containing a list of files to encode
+  ${BOLD}${YELLOW}-S, --skip-codec${ALL_OFF} ${BOLD}${GREEN}LIST${ALL_OFF}               skip files with these codecs;
+                                      ${BOLD}${GREEN}LIST${ALL_OFF} is comma, space, or colon separated
+      ${BOLD}${YELLOW}--skip-codec-override${ALL_OFF}           use only codecs from --skip-codec,
+                                      ignoring [skip].codecs from config
 
 ${BOLD}${BLUE}Size report options:${ALL_OFF}
-  ${BOLD}${YELLOW}-s, --size-report${ALL_OFF}             print size feedback and write a status TSV log
-      ${BOLD}${YELLOW}--no-size-report${ALL_OFF}          disable size reporting from config.toml
-      ${BOLD}${YELLOW}--size-report-file${ALL_OFF} ${BOLD}${GREEN}FILE${ALL_OFF}   path for the size report log (default: ${BOLD}${RED}%s${ALL_OFF})
+  ${BOLD}${YELLOW}-s, --size-report${ALL_OFF}                   print size feedback and write a status TSV log
+      ${BOLD}${YELLOW}--no-size-report${ALL_OFF}                disable size reporting from config.toml
+      ${BOLD}${YELLOW}--size-report-file${ALL_OFF} ${BOLD}${GREEN}FILE${ALL_OFF}         path for the size report log (default: ${BOLD}${RED}%s${ALL_OFF})
 
 ${BOLD}${BLUE}Output options:${ALL_OFF}
-      ${BOLD}${YELLOW}--ffmpeg-loglevel${ALL_OFF}         specify the loglevel to pass to ffmpeg (default: ${BOLD}${RED}fatal${ALL_OFF})
-  ${BOLD}${YELLOW}-q, --quiet${ALL_OFF}                   suppress all output; takes precedence over ${BOLD}${YELLOW}-v${ALL_OFF}
-  ${BOLD}${YELLOW}-v, --verbose${ALL_OFF}                 explain what is being done
-      ${BOLD}${YELLOW}--color${ALL_OFF}                   force colored output
-      ${BOLD}${YELLOW}--no-color${ALL_OFF}                disable colored output
+      ${BOLD}${YELLOW}--ffmpeg-loglevel${ALL_OFF}               specify the loglevel to pass to ffmpeg (default: ${BOLD}${RED}fatal${ALL_OFF})
+  ${BOLD}${YELLOW}-q, --quiet${ALL_OFF}                         suppress all output; takes precedence over ${BOLD}${YELLOW}-v${ALL_OFF}
+  ${BOLD}${YELLOW}-v, --verbose${ALL_OFF}                       explain what is being done
+      ${BOLD}${YELLOW}--color${ALL_OFF}                         force colored output
+      ${BOLD}${YELLOW}--no-color${ALL_OFF}                      disable colored output
 
 ${BOLD}${BLUE}General options:${ALL_OFF}
-  ${BOLD}${YELLOW}-h, --help${ALL_OFF}                    display this help and exit
-      ${BOLD}${YELLOW}--version${ALL_OFF}                 output version information and exit
-      ${BOLD}${YELLOW}--list-presets${ALL_OFF}            list available presets and exit
+  ${BOLD}${YELLOW}-h, --help${ALL_OFF}                          display this help and exit
+      ${BOLD}${YELLOW}--version${ALL_OFF}                       output version information and exit
+      ${BOLD}${YELLOW}--list-presets${ALL_OFF}                  list available presets and exit
 
 ${BOLD}${BLUE}Configuration files:${ALL_OFF}
   ${BOLD}${CYAN}%s/<NAME>.sh${ALL_OFF}
@@ -347,9 +350,14 @@ ${BOLD}${BLUE}Examples:${ALL_OFF}
   %s -n -N 10 my_movie.mkv\n" \
     "$SCRIPTNAME" "$VERSION" "$DESCRIPTION" \
     "$SCRIPTNAME" \
-    "$PRESET_NAME" "$NICE_VALUE" "$SIZE_REPORT_FILE" \
-    "$PRESET_DIR" "$CONFIG_FILE" \
-    "$SCRIPTNAME" "$SCRIPTNAME" "$SCRIPTNAME"
+    "$PRESET_NAME" \
+    "$NICE_VALUE" \
+    "$SIZE_REPORT_FILE" \
+    "$PRESET_DIR" \
+    "$CONFIG_FILE" \
+    "$SCRIPTNAME" \
+    "$SCRIPTNAME" \
+    "$SCRIPTNAME"
 }
 
 print_version() {
@@ -594,6 +602,20 @@ load_config() {
     fi
   fi
 
+  # [encoding] video_stream
+  if [[ $_CLI_VIDEO_STREAM -eq 0 ]]; then
+    val=$(_tomlq_get '.encoding.video_stream // empty')
+    if [[ -n "$val" ]]; then
+      debug "Config: encoding.video_stream =" "$val"
+      if ! validate_stream_selector "$val"; then
+        warning "Ignoring invalid config value for encoding.video_stream:" "$val"
+        warning "Falling back to default video stream:" "$VIDEO_STREAM"
+      else
+        VIDEO_STREAM="$val"
+      fi
+    fi
+  fi
+
   if [[ $_CLI_BACKUP_DIR -eq 0 ]]; then
     val=$(_tomlq_get '.encoding.backup_dir // empty')
     if [[ -n "$val" ]]; then
@@ -702,6 +724,22 @@ parse_skip_codec_parameter() {
 }
 
 ###############################################################################
+# STREAM SELECTOR HANDLING
+###############################################################################
+
+validate_stream_selector() {
+  local stream_selector="$1"
+
+  # Accept only simple video stream indexes for metadata probing. This is not a
+  # general ffmpeg stream selector parser.
+  if [[ ! "$stream_selector" =~ ^((v|V):)?([0-9]|[1-9][0-9]+)$ ]]; then
+    return 1
+  fi
+
+  return 0
+}
+
+###############################################################################
 # PRESET HANDLING
 ###############################################################################
 
@@ -1109,9 +1147,14 @@ encode_one() {
   # Probe codec, pixel format and frame rate in a single ffprobe invocation to
   # decrease the startup overhead on large batches.
   local probe_out
-  probe_out=$(ffprobe -v error -select_streams v:0 \
-    -show_entries stream=codec_name,pix_fmt,r_frame_rate \
-    -of default=nk=1:nw=1 "file:$input_file" 2>/dev/null)
+  probe_out=$(
+    ffprobe \
+      -v error \
+      -select_streams "$VIDEO_STREAM" \
+      -show_entries stream=codec_name,pix_fmt,r_frame_rate \
+      -of default=nk=1:nw=1 \
+      "file:$input_file" 2>/dev/null
+  )
 
   local input_codec input_pixel_format input_frame_rate input_fps
 
@@ -1267,6 +1310,7 @@ encode_one() {
 
   if [[ $DRY_RUN -eq 1 ]]; then
     msg "DRY RUN:" "Would encode with preset $PRESET_NAME"
+    verbose "Video stream:" "$VIDEO_STREAM"
     verbose "Input codec:" "$input_codec"
     verbose "Input pixel format:" "$input_pixel_format"
     verbose "Output pixel format:" "$output_pixel_format"
@@ -1675,6 +1719,36 @@ while [[ $# -gt 0 ]]; do
     _CLI_FFMPEG_LOGLEVEL=1
     shift
     ;;
+  --video-stream)
+    if [[ $# -lt 2 ]]; then
+      error "Missing value for:" "$1"
+      exit $EXIT_USAGE_ERROR
+    fi
+    if [[ ! -n "$2" ]]; then
+      error "Value for $1 must not be empty"
+      exit $EXIT_USAGE_ERROR
+    fi
+    if ! validate_stream_selector "$2"; then
+      error "Invalid stream selector:" "$2"
+      exit $EXIT_USAGE_ERROR
+    fi
+    VIDEO_STREAM="$2"
+    _CLI_VIDEO_STREAM=1
+    shift 2
+    ;;
+  --video-stream=*)
+    if [[ ! -n "${1#*=}" ]]; then
+      error "Value for --video-stream must not be empty"
+      exit $EXIT_USAGE_ERROR
+    fi
+    if ! validate_stream_selector "${1#*=}"; then
+      error "Invalid stream selector:" "${1#*=}"
+      exit $EXIT_USAGE_ERROR
+    fi
+    VIDEO_STREAM="${1#*=}"
+    _CLI_VIDEO_STREAM=1
+    shift
+    ;;
   --)
     shift
     REMAINING_ARGS+=("$@")
@@ -1722,6 +1796,7 @@ debug "  size-report:" "$SIZE_REPORT"
 debug "  skip-codecs:" "${joined# }"
 debug "  verbose:" "$VERBOSE"
 debug "  verify-output:" "$VERIFY_OUTPUT"
+debug "  video-stream:" "$VIDEO_STREAM"
 
 command -v ffmpeg >/dev/null 2>&1 || {
   error "ffmpeg not found."
diff --git a/transcode.sh.1 b/transcode.sh.1
index bc3639c..e0b7f3c 100644
--- a/transcode.sh.1
+++ b/transcode.sh.1
@@ -24,9 +24,13 @@ containing the extra arguments passed to
 .PP
 The script probes every input file with
 .BR ffprobe (1)
-to detect the input video codec and pixel format. Files whose codec
-appears in the skip list are silently skipped. The output pixel format
-is derived automatically so that chroma subsampling (4:2:0, 4:2:2,
+to detect the input video codec, pixel format and frame rate of the selected
+video probe stream. The selected stream defaults to
+.B v:0
+and can be changed with
+.BR \-\-video\-stream .
+Files whose codec appears in the skip list are silently skipped. The output
+pixel format is derived automatically so that chroma subsampling (4:2:0, 4:2:2,
 4:4:4) and bit depth (8, 10, 12, 16\-bit) are preserved.
 .PP
 All streams, metadata and chapter markers from the input are retained by
@@ -84,7 +88,8 @@ Print what would be done without actually invoking
 .BR ffmpeg (1).
 Combine with
 .B \-v
-to see the detected codec and pixel format information.
+to see the selected video stream and detected codec, pixel format and frame
+rate information.
 .TP
 .BR \-\-backup\-dir " \fIDIR\fR, " \-\-backup\-dir= \fIDIR\fR
 Copy originals to \fIDIR\fR before replacing them after successful encoding.
@@ -123,6 +128,17 @@ to
 Use this on hosts where hardware acceleration causes compatibility or
 stability issues.
 .TP
+.BR \-\-video\-stream " \fISTREAM_SELECTOR\fR, " \-\-video\-stream= \fISTREAM_SELECTOR\fR
+Select the input video stream that is probed for preset helper variables.
+Defaults to
+.BR v:0 .
+The selector must be a conservative video stream selector such as
+.B v:0
+or
+.BR v:1 .
+This option does not change ffmpeg stream mapping; presets remain responsible
+for selecting which stream to encode.
+.TP
 .BR \-N " \fIVALUE\fR, " \-\-nice " \fIVALUE\fR, " \-\-nice= \fIVALUE\fR
 Run
 .BR ffmpeg (1)
@@ -195,8 +211,8 @@ Suppress all normal output. Takes precedence over
 .BR \-v / \-\-verbose .
 .TP
 .BR \-v ", " \-\-verbose
-Emit additional informational messages (detected codec, pixel format,
-etc.).
+Emit additional informational messages, including the selected video stream and
+detected codec, pixel format and frame rate.
 .TP
 .B \-\-version
 Print version, author and license information and exit.
@@ -294,7 +310,15 @@ array variable named
 .B ffargs
 containing additional arguments for
 .BR ffmpeg (1).
-The following variables are available to presets at source time:
+These variables are derived from the selected video probe stream, which
+defaults to
+.B v:0
+and can be changed with
+.BR \-\-video\-stream
+or
+.B [encoding] video_stream
+in
+.BR config.toml .
 .RS
 .TP
 .B input_codec
@@ -418,6 +442,14 @@ encoding and before replacement. Equivalent to
 .BR \-\-backup\-dir .
 CLI \fB--backup-dir\fR takes precedence.
 .TP
+.B [encoding] video_stream
+String. Input video stream to probe for preset helper variables. Defaults to
+.BR v:0 .
+Equivalent to
+.BR \-\-video\-stream .
+Invalid configured values are ignored with a warning and the default is used.
+This setting does not change ffmpeg stream mapping in presets.
+.TP
 .B [skip] codecs
 Array of strings. Merged with any codecs from
 .BR \-S
@@ -538,6 +570,14 @@ Load an alternative configuration file:
 transcode.sh \-\-config\-file ~/profiles/fast.toml input.mp4
 .fi
 .RE
+.PP
+Probe the second video stream for preset helper variables:
+.PP
+.RS
+.nf
+transcode.sh \-\-video\-stream v:1 \-n \-v input.mkv
+.fi
+.RE
 .SH SEE ALSO
 .BR ffmpeg (1),
 .BR ffprobe (1),
diff --git a/transcode.sh.bash-completion b/transcode.sh.bash-completion
index 716995e..c980081 100644
--- a/transcode.sh.bash-completion
+++ b/transcode.sh.bash-completion
@@ -39,6 +39,7 @@ _transcode_sh() {
   local nice_vals='0 5 10 15 19'
   local hwaccel_methods='auto cuda vaapi dxva2 d3d11va videotoolbox qsv'
   local ffmpeg_loglevels='quiet panic fatal error warning info verbose debug trace'
+  local video_streams='v:0 v:1 v:2 v:3'
 
   # ---------------------------------------------------------------------------
   # Handle --option=VALUE: cur contains the entire "--opt=val" token.
@@ -91,6 +92,11 @@ _transcode_sh() {
     COMPREPLY=($(compgen -W "$ffmpeg_loglevels" -- "$cur"))
     return
     ;;
+  --video-stream=*)
+    cur="${cur#*=}"
+    COMPREPLY=($(compgen -W "$video_streams" -- "$cur"))
+    return
+    ;;
   esac
 
   # ---------------------------------------------------------------------------
@@ -135,6 +141,10 @@ _transcode_sh() {
     COMPREPLY=($(compgen -W "$ffmpeg_loglevels" -- "$cur"))
     return
     ;;
+  --video-stream)
+    COMPREPLY=($(compgen -W "$video_streams" -- "$cur"))
+    return
+    ;;
   esac
 
   # ---------------------------------------------------------------------------
@@ -183,6 +193,8 @@ _transcode_sh() {
       --verbose
       --verify-output
       --version
+      --video-stream
+      --video-stream=
     '
     COMPREPLY=($(compgen -W "$longopts" -- "$cur"))
     # Suppress the trailing space when the only completion ends with '='