command: add demuxer-lavf-list property

Was only available with --demuxer-lavf-format=help and the demuxer
needed to be used for it to actually print the list.

This can be used in the future to check if 'dash' support was compiled
with FFmpeg so ytdl_hook can use it instead. For now, dashdec is too
rudimentary to be used right away.

DOCS/man/input.rst

@@ -2119,6 +2119,10 @@ Property list
     The encoder names (``driver`` entries) can be passed to ``--ovc`` and
     ``--oac`` (without the ``lavc:`` prefix required by ``--vd`` and ``--ad``).
 
+``demuxer-lavf-list``
+    List of available libavformat demuxers' names. This can be used to check
+    for support for a specific format or use with ``--demuxer-lavf-format``.
+
 ``mpv-version``
     Return the mpv version/copyright string. Depending on how the binary was
     built, it might contain either a release version, or just a git hash.

common/av_common.c

@@ -26,13 +26,15 @@
 #include <libavutil/error.h>
 #include <libavutil/cpu.h>
 #include <libavcodec/avcodec.h>
+#include <libavformat/avformat.h>
 
 #include "config.h"
 
 #include "common/common.h"
 #include "common/msg.h"
 #include "demux/packet.h"
 #include "demux/stheader.h"
+#include "misc/bstr.h"
 #include "video/fmt-conversion.h"
 #include "av_common.h"
 #include "codecs.h"
@@ -246,6 +248,21 @@ void mp_add_lavc_encoders(struct mp_decoder_list *list)
     }
 }
 
+char **mp_get_lavf_demuxers(void)
+{
+    char **list = NULL;
+    AVInputFormat *cur = NULL;
+    int num = 0;
+    for (;;) {
+        cur = av_iformat_next(cur);
+        if (!cur)
+            break;
+        MP_TARRAY_APPEND(NULL, list, num, talloc_strdup(NULL, cur->name));
+    }
+    MP_TARRAY_APPEND(NULL, list, num, NULL);
+    return list;
+}
+
 int mp_codec_to_av_codec_id(const char *codec)
 {
     int id = AV_CODEC_ID_NONE;

common/av_common.h

@@ -41,6 +41,7 @@ double mp_pts_from_av(int64_t av_pts, AVRational *tb);
 void mp_set_avcodec_threads(struct mp_log *l, AVCodecContext *avctx, int threads);
 void mp_add_lavc_decoders(struct mp_decoder_list *list, enum AVMediaType type);
 void mp_add_lavc_encoders(struct mp_decoder_list *list);
+char **mp_get_lavf_demuxers(void);
 int mp_codec_to_av_codec_id(const char *codec);
 const char *mp_codec_from_av_codec_id(int codec_id);
 void mp_set_avdict(struct AVDictionary **dict, char **kv);

player/command.c

@@ -3588,6 +3588,20 @@ static int mp_property_encoders(void *ctx, struct m_property *prop,
     return r;
 }
 
+static int mp_property_lavf_demuxers(void *ctx, struct m_property *prop,
+                                 int action, void *arg)
+{
+    switch (action) {
+    case M_PROPERTY_GET:
+        *(char ***)arg = mp_get_lavf_demuxers();
+        return M_PROPERTY_OK;
+    case M_PROPERTY_GET_TYPE:
+        *(struct m_option *)arg = (struct m_option){.type = CONF_TYPE_STRING_LIST};
+        return M_PROPERTY_OK;
+    }
+    return M_PROPERTY_NOT_IMPLEMENTED;
+}
+
 static int mp_property_version(void *ctx, struct m_property *prop,
                                int action, void *arg)
 {
@@ -4027,6 +4041,7 @@ static const struct m_property mp_properties_base[] = {
     {"protocol-list", mp_property_protocols},
     {"decoder-list", mp_property_decoders},
     {"encoder-list", mp_property_encoders},
+    {"demuxer-lavf-list", mp_property_lavf_demuxers},
 
     {"mpv-version", mp_property_version},
     {"mpv-configuration", mp_property_configuration},