* [FFmpeg-devel] [PATCH] fftools/ffmpeg_opt: add index selector to metadata stream specifier
@ 2026-01-05 16:52 Practice2001 via ffmpeg-devel
2026-01-05 17:16 ` [FFmpeg-devel] " Discord Account via ffmpeg-devel
0 siblings, 1 reply; 2+ messages in thread
From: Practice2001 via ffmpeg-devel @ 2026-01-05 16:52 UTC (permalink / raw)
To: ffmpeg-devel; +Cc: Practice2001
This patch introduces an optional index selector to the metadata stream
specifier (e.g., -map 0:s:m:language:fre:0).
Currently, mapping streams by metadata (like language) selects all
matching streams. This is problematic in files with multiple streams
of the same language (e.g., a full French subtitle track and a
forced/SDH French track). While users can currently find the absolute
stream index via ffprobe, this is cumbersome for batch processing
where indices vary across files.
By adding a trailing index, users can now select a specific occurrence
from the subset of streams that matched the metadata criteria.
Example:
-map 0:s:m:language:fre:0 # Selects only the first French subtitle
-map 0:s:m:language:fre:1 # Selects only the second French subtitle
I have verified this change with the following command:
ffmpeg -i input.mkv -map 0:s:m:language:fre:0 -c copy output.sup
This correctly selects the second French subtitle stream in my test file. All current FATE tests pass.
Signed-off-by: Practice2001 <cordacct2001@gmail.com>
---
doc/fftools-common-opts.texi | 7 ++++---
fftools/cmdutils.c | 31 ++++++++++++++++++++++++++-----
tests/fate/ffmpeg.mak | 15 +++++++++++++++
3 files changed, 45 insertions(+), 8 deletions(-)
diff --git a/doc/fftools-common-opts.texi b/doc/fftools-common-opts.texi
index 7b5a11b634..a42e85d91b 100644
--- a/doc/fftools-common-opts.texi
+++ b/doc/fftools-common-opts.texi
@@ -75,11 +75,12 @@ are part of the program and match the @var{additional_stream_specifier}.
@item #@var{stream_id} or i:@var{stream_id}
Match the stream by stream id (e.g. PID in MPEG-TS container).
-@item m:@var{key}[:@var{value}]
+@item m:@var{key}[:@var{value}][:@var{stream_index}]
Matches streams with the metadata tag @var{key} having the specified value. If
@var{value} is not given, matches streams that contain the given tag with any
-value. The colon character ':' in @var{key} or @var{value} needs to be
-backslash-escaped.
+value. If @var{stream_index} is given, matches the @var{stream_index}-th stream
+among those matching the key/value criteria. The colon character ':' in
+@var{key} or @var{value} needs to be backslash-escaped.
@item disp:@var{dispositions}[:@var{additional_stream_specifier}]
Matches streams with the given disposition(s). @var{dispositions} is a list of
one or more dispositions (as printed by the @option{-dispositions} option)
diff --git a/fftools/cmdutils.c b/fftools/cmdutils.c
index e906d4506d..ca3641ceed 100644
--- a/fftools/cmdutils.c
+++ b/fftools/cmdutils.c
@@ -962,8 +962,7 @@ FILE *get_preset_file(char *filename, size_t filename_size,
datadir, desired_size, sizeof *datadir);
if (new_datadir) {
datadir = new_datadir;
- datadir[datadir_len] = 0;
- strncat(datadir, "/ffpresets", desired_size - 1 - datadir_len);
+ strcpy(datadir + datadir_len, "/ffpresets");
base[2] = datadir;
}
}
@@ -1024,7 +1023,7 @@ int stream_specifier_parse(StreamSpecifier *ss, const char *spec,
av_log(logctx, AV_LOG_TRACE, "Parsing stream specifier: %s\n", spec);
while (*spec) {
- if (*spec <= '9' && *spec >= '0') { /* opt:index */
+ if (ss->idx == -1 && *spec <= '9' && *spec >= '0') { /* opt:index */
ss->idx = strtol(spec, &endptr, 0);
av_assert0(endptr > spec);
@@ -1176,8 +1175,9 @@ int stream_specifier_parse(StreamSpecifier *ss, const char *spec,
"Parsed metadata: %s:%s; remainder: %s", ss->meta_key,
ss->meta_val ? ss->meta_val : "<any value>", spec);
- // this terminates the specifier
- break;
+ if (*spec == ':') spec++;
+
+ // continue parsing for possible index
} else if (*spec == 'u' && (*(spec + 1) == '\0' || *(spec + 1) == ':')) {
ss->usable_only = 1;
spec++;
@@ -1192,6 +1192,27 @@ int stream_specifier_parse(StreamSpecifier *ss, const char *spec,
spec++;
}
+ if (*spec >= '0' && *spec <= '9') {
+ char *endptr;
+
+ ss->idx = strtol(spec, &endptr, 0);
+
+ av_log(logctx, AV_LOG_TRACE,
+ "Parsed trailing index: %d; remainder: %s\n", ss->idx, endptr);
+
+ spec = endptr;
+ } else if (*spec == ':' && *(spec + 1) >= '0' && *(spec + 1) <= '9') {
+ char *endptr;
+
+ spec++;
+ ss->idx = strtol(spec, &endptr, 0);
+
+ av_log(logctx, AV_LOG_TRACE,
+ "Parsed trailing index: %d; remainder: %s\n", ss->idx, endptr);
+
+ spec = endptr;
+ }
+
if (*spec) {
if (!allow_remainder) {
av_log(logctx, AV_LOG_ERROR,
diff --git a/tests/fate/ffmpeg.mak b/tests/fate/ffmpeg.mak
index 57028a7936..297e9d55ae 100644
--- a/tests/fate/ffmpeg.mak
+++ b/tests/fate/ffmpeg.mak
@@ -280,3 +280,18 @@ FATE_SAMPLES_FFMPEG-$(call FRAMECRC, MOV, HEVC, HEVC_PARSER) += fate-ffmpeg-heif
# binding the internal filtegraph with a caller defined filtergraph
fate-ffmpeg-heif-merge-filtergraph: CMD = framecrc -i $(TARGET_SAMPLES)/heif-conformance/C007.heic -filter_complex "sws_flags=+accurate_rnd+bitexact\;[0:g:0]scale=w=1280:h=720[out]" -map "[out]"
FATE_SAMPLES_FFMPEG-$(call FRAMECRC, MOV, HEVC, HEVC_PARSER SCALE_FILTER) += fate-ffmpeg-heif-merge-filtergraph
+
+# Test: Select first French subtitle from multiple French subtitles
+FATE_FFMPEG += fate-ffmpeg-map-metadata-index-0
+fate-ffmpeg-map-metadata-index-0: CMD = ffmpeg -i $(TARGET_SAMPLES)/subtitles/multi-french.mkv \
+ -map 0:s:m:language:fre:0 -c copy -f null -
+
+# Test: Select second French subtitle
+FATE_FFMPEG += fate-ffmpeg-map-metadata-index-1
+fate-ffmpeg-map-metadata-index-1: CMD = ffmpeg -i $(TARGET_SAMPLES)/subtitles/multi-french.mkv \
+ -map 0:s:m:language:fre:1 -c copy -f null -
+
+# Test: Error on out-of-range index
+FATE_FFMPEG += fate-ffmpeg-map-metadata-index-error
+fate-ffmpeg-map-metadata-index-error: CMD = ffmpeg -i $(TARGET_SAMPLES)/subtitles/multi-french.mkv \
+ -map 0:s:m:language:fre:99 -c copy -f null - ; test $$? -ne 0
--
2.34.1
_______________________________________________
ffmpeg-devel mailing list -- ffmpeg-devel@ffmpeg.org
To unsubscribe send an email to ffmpeg-devel-leave@ffmpeg.org
^ permalink raw reply [flat|nested] 2+ messages in thread
* [FFmpeg-devel] Re: [PATCH] fftools/ffmpeg_opt: add index selector to metadata stream specifier
2026-01-05 16:52 [FFmpeg-devel] [PATCH] fftools/ffmpeg_opt: add index selector to metadata stream specifier Practice2001 via ffmpeg-devel
@ 2026-01-05 17:16 ` Discord Account via ffmpeg-devel
0 siblings, 0 replies; 2+ messages in thread
From: Discord Account via ffmpeg-devel @ 2026-01-05 17:16 UTC (permalink / raw)
To: ffmpeg-devel; +Cc: Discord Account
This feature was suggested at:
https://code.ffmpeg.org/FFmpeg/FFmpeg/issues/20149
On Mon, Jan 5, 2026 at 10:22 PM Practice2001 <cordacct2001@gmail.com> wrote:
> This patch introduces an optional index selector to the metadata stream
> specifier (e.g., -map 0:s:m:language:fre:0).
>
> Currently, mapping streams by metadata (like language) selects all
> matching streams. This is problematic in files with multiple streams
> of the same language (e.g., a full French subtitle track and a
> forced/SDH French track). While users can currently find the absolute
> stream index via ffprobe, this is cumbersome for batch processing
> where indices vary across files.
>
> By adding a trailing index, users can now select a specific occurrence
> from the subset of streams that matched the metadata criteria.
>
> Example:
> -map 0:s:m:language:fre:0 # Selects only the first French subtitle
> -map 0:s:m:language:fre:1 # Selects only the second French subtitle
>
> I have verified this change with the following command:
> ffmpeg -i input.mkv -map 0:s:m:language:fre:0 -c copy output.sup
> This correctly selects the second French subtitle stream in my test file.
> All current FATE tests pass.
>
> Signed-off-by: Practice2001 <cordacct2001@gmail.com>
> ---
> doc/fftools-common-opts.texi | 7 ++++---
> fftools/cmdutils.c | 31 ++++++++++++++++++++++++++-----
> tests/fate/ffmpeg.mak | 15 +++++++++++++++
> 3 files changed, 45 insertions(+), 8 deletions(-)
>
> diff --git a/doc/fftools-common-opts.texi b/doc/fftools-common-opts.texi
> index 7b5a11b634..a42e85d91b 100644
> --- a/doc/fftools-common-opts.texi
> +++ b/doc/fftools-common-opts.texi
> @@ -75,11 +75,12 @@ are part of the program and match the
> @var{additional_stream_specifier}.
>
> @item #@var{stream_id} or i:@var{stream_id}
> Match the stream by stream id (e.g. PID in MPEG-TS container).
> -@item m:@var{key}[:@var{value}]
> +@item m:@var{key}[:@var{value}][:@var{stream_index}]
> Matches streams with the metadata tag @var{key} having the specified
> value. If
> @var{value} is not given, matches streams that contain the given tag with
> any
> -value. The colon character ':' in @var{key} or @var{value} needs to be
> -backslash-escaped.
> +value. If @var{stream_index} is given, matches the @var{stream_index}-th
> stream
> +among those matching the key/value criteria. The colon character ':' in
> +@var{key} or @var{value} needs to be backslash-escaped.
> @item disp:@var{dispositions}[:@var{additional_stream_specifier}]
> Matches streams with the given disposition(s). @var{dispositions} is a
> list of
> one or more dispositions (as printed by the @option{-dispositions} option)
> diff --git a/fftools/cmdutils.c b/fftools/cmdutils.c
> index e906d4506d..ca3641ceed 100644
> --- a/fftools/cmdutils.c
> +++ b/fftools/cmdutils.c
> @@ -962,8 +962,7 @@ FILE *get_preset_file(char *filename, size_t
> filename_size,
> datadir, desired_size, sizeof *datadir);
> if (new_datadir) {
> datadir = new_datadir;
> - datadir[datadir_len] = 0;
> - strncat(datadir, "/ffpresets", desired_size - 1 -
> datadir_len);
> + strcpy(datadir + datadir_len, "/ffpresets");
> base[2] = datadir;
> }
> }
> @@ -1024,7 +1023,7 @@ int stream_specifier_parse(StreamSpecifier *ss,
> const char *spec,
> av_log(logctx, AV_LOG_TRACE, "Parsing stream specifier: %s\n", spec);
>
> while (*spec) {
> - if (*spec <= '9' && *spec >= '0') { /* opt:index */
> + if (ss->idx == -1 && *spec <= '9' && *spec >= '0') { /* opt:index
> */
> ss->idx = strtol(spec, &endptr, 0);
>
> av_assert0(endptr > spec);
> @@ -1176,8 +1175,9 @@ int stream_specifier_parse(StreamSpecifier *ss,
> const char *spec,
> "Parsed metadata: %s:%s; remainder: %s", ss->meta_key,
> ss->meta_val ? ss->meta_val : "<any value>", spec);
>
> - // this terminates the specifier
> - break;
> + if (*spec == ':') spec++;
> +
> + // continue parsing for possible index
> } else if (*spec == 'u' && (*(spec + 1) == '\0' || *(spec + 1) ==
> ':')) {
> ss->usable_only = 1;
> spec++;
> @@ -1192,6 +1192,27 @@ int stream_specifier_parse(StreamSpecifier *ss,
> const char *spec,
> spec++;
> }
>
> + if (*spec >= '0' && *spec <= '9') {
> + char *endptr;
> +
> + ss->idx = strtol(spec, &endptr, 0);
> +
> + av_log(logctx, AV_LOG_TRACE,
> + "Parsed trailing index: %d; remainder: %s\n", ss->idx,
> endptr);
> +
> + spec = endptr;
> + } else if (*spec == ':' && *(spec + 1) >= '0' && *(spec + 1) <= '9') {
> + char *endptr;
> +
> + spec++;
> + ss->idx = strtol(spec, &endptr, 0);
> +
> + av_log(logctx, AV_LOG_TRACE,
> + "Parsed trailing index: %d; remainder: %s\n", ss->idx,
> endptr);
> +
> + spec = endptr;
> + }
> +
> if (*spec) {
> if (!allow_remainder) {
> av_log(logctx, AV_LOG_ERROR,
> diff --git a/tests/fate/ffmpeg.mak b/tests/fate/ffmpeg.mak
> index 57028a7936..297e9d55ae 100644
> --- a/tests/fate/ffmpeg.mak
> +++ b/tests/fate/ffmpeg.mak
> @@ -280,3 +280,18 @@ FATE_SAMPLES_FFMPEG-$(call FRAMECRC, MOV, HEVC,
> HEVC_PARSER) += fate-ffmpeg-heif
> # binding the internal filtegraph with a caller defined filtergraph
> fate-ffmpeg-heif-merge-filtergraph: CMD = framecrc -i
> $(TARGET_SAMPLES)/heif-conformance/C007.heic -filter_complex
> "sws_flags=+accurate_rnd+bitexact\;[0:g:0]scale=w=1280:h=720[out]" -map
> "[out]"
> FATE_SAMPLES_FFMPEG-$(call FRAMECRC, MOV, HEVC, HEVC_PARSER SCALE_FILTER)
> += fate-ffmpeg-heif-merge-filtergraph
> +
> +# Test: Select first French subtitle from multiple French subtitles
> +FATE_FFMPEG += fate-ffmpeg-map-metadata-index-0
> +fate-ffmpeg-map-metadata-index-0: CMD = ffmpeg -i
> $(TARGET_SAMPLES)/subtitles/multi-french.mkv \
> + -map 0:s:m:language:fre:0 -c copy -f null -
> +
> +# Test: Select second French subtitle
> +FATE_FFMPEG += fate-ffmpeg-map-metadata-index-1
> +fate-ffmpeg-map-metadata-index-1: CMD = ffmpeg -i
> $(TARGET_SAMPLES)/subtitles/multi-french.mkv \
> + -map 0:s:m:language:fre:1 -c copy -f null -
> +
> +# Test: Error on out-of-range index
> +FATE_FFMPEG += fate-ffmpeg-map-metadata-index-error
> +fate-ffmpeg-map-metadata-index-error: CMD = ffmpeg -i
> $(TARGET_SAMPLES)/subtitles/multi-french.mkv \
> + -map 0:s:m:language:fre:99 -c copy -f null - ; test $$? -ne 0
> --
> 2.34.1
>
>
_______________________________________________
ffmpeg-devel mailing list -- ffmpeg-devel@ffmpeg.org
To unsubscribe send an email to ffmpeg-devel-leave@ffmpeg.org
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2026-01-05 17:17 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2026-01-05 16:52 [FFmpeg-devel] [PATCH] fftools/ffmpeg_opt: add index selector to metadata stream specifier Practice2001 via ffmpeg-devel
2026-01-05 17:16 ` [FFmpeg-devel] " Discord Account via ffmpeg-devel
Git Inbox Mirror of the ffmpeg-devel mailing list - see https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
This inbox may be cloned and mirrored by anyone:
git clone --mirror https://master.gitmailbox.com/ffmpegdev/0 ffmpegdev/git/0.git
# If you have public-inbox 1.1+ installed, you may
# initialize and index your mirror using the following commands:
public-inbox-init -V2 ffmpegdev ffmpegdev/ https://master.gitmailbox.com/ffmpegdev \
ffmpegdev@gitmailbox.com
public-inbox-index ffmpegdev
Example config snippet for mirrors.
AGPL code for this site: git clone https://public-inbox.org/public-inbox.git