fftools/ffmpeg: deprecate the -map_channel option

It is now entirely redundant with audio filters, and is in fact
implemented by setting up a 'pan' filter instance.

doc/ffmpeg.texi

@@ -1492,6 +1492,10 @@ Allow input streams with unknown type to be copied instead of failing if copying
 such streams is attempted.
 
 @item -map_channel [@var{input_file_id}.@var{stream_specifier}.@var{channel_id}|-1][?][:@var{output_file_id}.@var{stream_specifier}]
+This option is deprecated and will be removed. It can be replaced by the
+@var{pan} filter. In some cases it may be easier to use some combination of the
+@var{channelsplit}, @var{channelmap}, or @var{amerge} filters.
+
 Map an audio channel from a given input to an output. If
 @var{output_file_id}.@var{stream_specifier} is not set, the audio channel will
 be mapped on all the audio streams.

fftools/ffmpeg.c

@@ -578,8 +578,10 @@ static void ffmpeg_cleanup(int ret)
         av_freep(&ost->avfilter);
         av_freep(&ost->logfile_prefix);
 
+#if FFMPEG_OPT_MAP_CHANNEL
         av_freep(&ost->audio_channels_map);
         ost->audio_channels_mapped = 0;
+#endif
 
         av_dict_free(&ost->sws_dict);
         av_dict_free(&ost->swr_opts);

fftools/ffmpeg.h

@@ -51,6 +51,7 @@
 
 // deprecated features
 #define FFMPEG_OPT_PSNR 1
+#define FFMPEG_OPT_MAP_CHANNEL 1
 
 enum VideoSyncMethod {
     VSYNC_AUTO = -1,
@@ -85,10 +86,12 @@ typedef struct StreamMap {
     char *linklabel;       /* name of an output link, for mapping lavfi outputs */
 } StreamMap;
 
+#if FFMPEG_OPT_MAP_CHANNEL
 typedef struct {
     int  file_idx,  stream_idx,  channel_idx; // input
     int ofile_idx, ostream_idx;               // output
 } AudioChannelMap;
+#endif
 
 typedef struct OptionsContext {
     OptionGroup *g;
@@ -141,8 +144,10 @@ typedef struct OptionsContext {
     /* output options */
     StreamMap *stream_maps;
     int     nb_stream_maps;
+#if FFMPEG_OPT_MAP_CHANNEL
     AudioChannelMap *audio_channel_maps; /* one info entry per -map_channel */
     int           nb_audio_channel_maps; /* number of (valid) -map_channel settings */
+#endif
     int metadata_global_manual;
     int metadata_streams_manual;
     int metadata_chapters_manual;
@@ -516,8 +521,10 @@ typedef struct OutputStream {
     int dropped_keyframe;
 
     /* audio only */
+#if FFMPEG_OPT_MAP_CHANNEL
     int *audio_channels_map;             /* list of the channels id to pick from the source stream */
     int audio_channels_mapped;           /* number of channels in audio_channels_map */
+#endif
 
     char *logfile_prefix;
     FILE *logfile;

fftools/ffmpeg_filter.c

@@ -560,6 +560,7 @@ static int configure_output_audio_filter(FilterGraph *fg, OutputFilter *ofilter,
     pad_idx = 0;                                                            \
 } while (0)
     av_bprint_init(&args, 0, AV_BPRINT_SIZE_UNLIMITED);
+#if FFMPEG_OPT_MAP_CHANNEL
     if (ost->audio_channels_mapped) {
         AVChannelLayout mapped_layout = { 0 };
         int i;
@@ -572,6 +573,7 @@ static int configure_output_audio_filter(FilterGraph *fg, OutputFilter *ofilter,
         AUTO_INSERT_FILTER("-map_channel", "pan", args.str);
         av_bprint_clear(&args);
     }
+#endif
 
     if (codec->ch_layout.order == AV_CHANNEL_ORDER_UNSPEC)
         av_channel_layout_default(&codec->ch_layout, codec->ch_layout.nb_channels);

fftools/ffmpeg_opt.c

@@ -219,7 +219,9 @@ static void uninit_options(OptionsContext *o)
     for (i = 0; i < o->nb_stream_maps; i++)
         av_freep(&o->stream_maps[i].linklabel);
     av_freep(&o->stream_maps);
+#if FFMPEG_OPT_MAP_CHANNEL
     av_freep(&o->audio_channel_maps);
+#endif
     av_freep(&o->streamid_map);
     av_freep(&o->attachments);
 }
@@ -534,6 +536,7 @@ static int opt_attach(void *optctx, const char *opt, const char *arg)
     return 0;
 }
 
+#if FFMPEG_OPT_MAP_CHANNEL
 static int opt_map_channel(void *optctx, const char *opt, const char *arg)
 {
     OptionsContext *o = optctx;
@@ -542,6 +545,12 @@ static int opt_map_channel(void *optctx, const char *opt, const char *arg)
     AudioChannelMap *m;
     char *allow_unused;
     char *mapchan;
+
+    av_log(NULL, AV_LOG_WARNING,
+           "The -%s option is deprecated and will be removed. "
+           "It can be replaced by the 'pan' filter, or in some cases by "
+           "combinations of 'channelsplit', 'channelmap', 'amerge' filters.\n", opt);
+
     mapchan = av_strdup(arg);
     if (!mapchan)
         return AVERROR(ENOMEM);
@@ -610,6 +619,7 @@ static int opt_map_channel(void *optctx, const char *opt, const char *arg)
     av_free(mapchan);
     return 0;
 }
+#endif
 
 static int opt_sdp_file(void *optctx, const char *opt, const char *arg)
 {
@@ -2061,7 +2071,6 @@ static OutputStream *new_video_stream(OptionsContext *o, AVFormatContext *oc, in
 
 static OutputStream *new_audio_stream(OptionsContext *o, AVFormatContext *oc, int source_index)
 {
-    int n;
     AVStream *st;
     OutputStream *ost;
 
@@ -2121,8 +2130,9 @@ static OutputStream *new_audio_stream(OptionsContext *o, AVFormatContext *oc, in
         if (!ost->avfilter)
             exit_program(1);
 
+#if FFMPEG_OPT_MAP_CHANNEL
         /* check for channel mapping for this audio stream */
-        for (n = 0; n < o->nb_audio_channel_maps; n++) {
+        for (int n = 0; n < o->nb_audio_channel_maps; n++) {
             AudioChannelMap *map = &o->audio_channel_maps[n];
             if ((map->ofile_idx   == -1 || ost->file_index == map->ofile_idx) &&
                 (map->ostream_idx == -1 || ost->st->index  == map->ostream_idx)) {
@@ -2149,6 +2159,7 @@ static OutputStream *new_audio_stream(OptionsContext *o, AVFormatContext *oc, in
                 }
             }
         }
+#endif
     }
 
     if (ost->stream_copy)
@@ -3759,8 +3770,10 @@ const OptionDef options[] = {
                         OPT_OUTPUT,                                  { .func_arg = opt_map },
         "set input stream mapping",
         "[-]input_file_id[:stream_specifier][,sync_file_id[:stream_specifier]]" },
+#if FFMPEG_OPT_MAP_CHANNEL
     { "map_channel",    HAS_ARG | OPT_EXPERT | OPT_PERFILE | OPT_OUTPUT, { .func_arg = opt_map_channel },
-        "map an audio channel from one stream to another", "file.stream.channel[:syncfile.syncstream]" },
+        "map an audio channel from one stream to another (deprecated)", "file.stream.channel[:syncfile.syncstream]" },
+#endif
     { "map_metadata",   HAS_ARG | OPT_STRING | OPT_SPEC |
                         OPT_OUTPUT,                                  { .off       = OFFSET(metadata_map) },
         "set metadata information of outfile from infile",