stream_dvb: allow to enforce DVB-S/T for old zap format channels.conf

If a card supports both DVB-T/T2 or DVB-S/S2, channels.conf.{sat,ter}
was always interpreted as DVB-T2 / DVB-S2 before this change.
After this change, using channels.conf.{sat1,ter1} will enforce
interpretation as DVB-S/T.
The superior VDR channel config format is still the recommended solution
for such cards as it allows to specify the delivery system variant per
channel, but enforcing T2/S2 for cards supporting it whenever the zap
format is used does not seem reasonable.

DOCS/man/options.rst

@@ -5623,8 +5623,11 @@ DVB
 ``--dvbin-file=<filename>``
     Instructs mpv to read the channels list from ``<filename>``. The default is
     in the mpv configuration directory (usually ``~/.config/mpv``) with the
-    filename ``channels.conf.{sat,ter,cbl,atsc,isdbt}`` (based on your card
-    type) or ``channels.conf`` as a last resort.
+    filename ``channels.conf.{sat,sat1,ter,ter1,cbl,atsc,isdbt}`` (based on your
+    card type) or ``channels.conf`` as a last resort.
+    For cards supporting multiple delivery systems of the same kind, i.e.
+    DVB-T/T2 or DVB-S/S2, T2/S2 is assumed, unless the file extension
+    is ``ter1`` or ``sat1``.
     Please note that using specific file name with card type is recommended,
     since the legacy channel format is not fully standardized
     so autodetection of the delivery system may fail otherwise.

stream/stream_dvb.c

@@ -1090,9 +1090,12 @@ dvb_state_t *dvb_get_state(stream_t *stream)
                     conf_file_name = "channels.conf.atsc";
                     break;
                 case SYS_DVBT:
-                    if (DELSYS_IS_SET(delsys_mask[f], SYS_DVBT2))
-                        continue; /* Add all channels later with T2. */
-                    conf_file_name = "channels.conf.ter";
+                    if (DELSYS_IS_SET(delsys_mask[f], SYS_DVBT2)) {
+                        // only if ter1 is present, interpret as DVB-T, else will be loaded as DVB-T2
+                        conf_file_name = "channels.conf.ter1";
+                    } else {
+                        conf_file_name = "channels.conf.ter";
+                    }
                     break;
                 case SYS_DVBT2:
                     conf_file_name = "channels.conf.ter";
@@ -1101,9 +1104,12 @@ dvb_state_t *dvb_get_state(stream_t *stream)
                     conf_file_name = "channels.conf.isdbt";
                     break;
                 case SYS_DVBS:
-                    if (DELSYS_IS_SET(delsys_mask[f], SYS_DVBS2))
-                        continue; /* Add all channels later with S2. */
-                    conf_file_name = "channels.conf.sat";
+                    if (DELSYS_IS_SET(delsys_mask[f], SYS_DVBS2)) {
+                        // only if sat1 is present, interpret as DVB-S, else will be loaded as DVB-S2
+                        conf_file_name = "channels.conf.sat1";
+                    } else {
+                        conf_file_name = "channels.conf.sat";
+                    }
                     break;
                 case SYS_DVBS2:
                     conf_file_name = "channels.conf.sat";