fftools: Switch to const AVCodec * where possible

The obstacle to do so was in filter_codec_opts: It uses searches
the AVCodec for options via the AV_OPT_SEARCH_FAKE_OBJ method, which
requires using a void * that points to a pointer to a const AVClass.
When using const AVCodec *, one can not simply use a pointer that points
to the AVCodec's pointer to its AVClass, as said pointer is const, too.
This is fixed by using a temporary pointer to the AVClass.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

fftools/cmdutils.c

@@ -2101,7 +2101,7 @@ int check_stream_specifier(AVFormatContext *s, AVStream *st, const char *spec)
 }
 
 AVDictionary *filter_codec_opts(AVDictionary *opts, enum AVCodecID codec_id,
-                                AVFormatContext *s, AVStream *st, AVCodec *codec)
+                                AVFormatContext *s, AVStream *st, const AVCodec *codec)
 {
     AVDictionary    *ret = NULL;
     AVDictionaryEntry *t = NULL;
@@ -2130,6 +2130,7 @@ AVDictionary *filter_codec_opts(AVDictionary *opts, enum AVCodecID codec_id,
     }
 
     while (t = av_dict_get(opts, "", t, AV_DICT_IGNORE_SUFFIX)) {
+        const AVClass *priv_class;
         char *p = strchr(t->key, ':');
 
         /* check stream specification in opt name */
@@ -2142,8 +2143,8 @@ AVDictionary *filter_codec_opts(AVDictionary *opts, enum AVCodecID codec_id,
 
         if (av_opt_find(&cc, t->key, NULL, flags, AV_OPT_SEARCH_FAKE_OBJ) ||
             !codec ||
-            (codec->priv_class &&
-             av_opt_find(&codec->priv_class, t->key, NULL, flags,
+            ((priv_class = codec->priv_class) &&
+             av_opt_find(&priv_class, t->key, NULL, flags,
                          AV_OPT_SEARCH_FAKE_OBJ)))
             av_dict_set(&ret, t->key, t->value, 0);
         else if (t->key[0] == prefix &&

fftools/cmdutils.h

@@ -414,7 +414,7 @@ int check_stream_specifier(AVFormatContext *s, AVStream *st, const char *spec);
  * @return a pointer to the created dictionary
  */
 AVDictionary *filter_codec_opts(AVDictionary *opts, enum AVCodecID codec_id,
-                                AVFormatContext *s, AVStream *st, AVCodec *codec);
+                                AVFormatContext *s, AVStream *st, const AVCodec *codec);
 
 /**
  * Setup AVCodecContext options for avformat_find_stream_info().

fftools/ffmpeg.c

@@ -688,7 +688,7 @@ void assert_avoptions(AVDictionary *m)
     }
 }
 
-static void abort_codec_experimental(AVCodec *c, int encoder)
+static void abort_codec_experimental(const AVCodec *c, int encoder)
 {
     exit_program(1);
 }
@@ -2943,7 +2943,7 @@ static int init_input_stream(int ist_index, char *error, int error_len)
     InputStream *ist = input_streams[ist_index];
 
     if (ist->decoding_needed) {
-        AVCodec *codec = ist->dec;
+        const AVCodec *codec = ist->dec;
         if (!codec) {
             snprintf(error, error_len, "Decoder (codec %s) not found for input stream #%d:%d",
                     avcodec_get_name(ist->dec_ctx->codec_id), ist->file_index, ist->st->index);
@@ -3522,7 +3522,7 @@ static int init_output_stream(OutputStream *ost, AVFrame *frame,
     int ret = 0;
 
     if (ost->encoding_needed) {
-        AVCodec      *codec = ost->enc;
+        const AVCodec *codec = ost->enc;
         AVCodecContext *dec = NULL;
         InputStream *ist;
 

fftools/ffmpeg.h

@@ -307,7 +307,7 @@ typedef struct InputStream {
 #define DECODING_FOR_FILTER 2
 
     AVCodecContext *dec_ctx;
-    AVCodec *dec;
+    const AVCodec *dec;
     AVFrame *decoded_frame;
     AVFrame *filter_frame; /* a ref of decoded_frame, to be sent to filters */
 
@@ -470,7 +470,7 @@ typedef struct OutputStream {
 
     AVCodecContext *enc_ctx;
     AVCodecParameters *ref_par; /* associated input codec parameters with encoders options applied */
-    AVCodec *enc;
+    const AVCodec *enc;
     int64_t max_frames;
     AVFrame *filtered_frame;
     AVFrame *last_frame;

fftools/ffmpeg_opt.c

@@ -766,13 +766,13 @@ static AVCodec *find_codec_or_die(const char *name, enum AVMediaType type, int e
     return codec;
 }
 
-static AVCodec *choose_decoder(OptionsContext *o, AVFormatContext *s, AVStream *st)
+static const AVCodec *choose_decoder(OptionsContext *o, AVFormatContext *s, AVStream *st)
 {
     char *codec_name = NULL;
 
     MATCH_PER_STREAM_OPT(codec_names, str, codec_name, s, st);
     if (codec_name) {
-        AVCodec *codec = find_codec_or_die(codec_name, st->codecpar->codec_type, 0);
+        const AVCodec *codec = find_codec_or_die(codec_name, st->codecpar->codec_type, 0);
         st->codecpar->codec_id = codec->id;
         return codec;
     } else

fftools/ffplay.c

@@ -2573,7 +2573,7 @@ static int stream_component_open(VideoState *is, int stream_index)
 {
     AVFormatContext *ic = is->ic;
     AVCodecContext *avctx;
-    AVCodec *codec;
+    const AVCodec *codec;
     const char *forced_codec_name = NULL;
     AVDictionary *opts = NULL;
     AVDictionaryEntry *t = NULL;

fftools/ffprobe.c

@@ -2996,7 +2996,7 @@ static int open_input_file(InputFile *ifile, const char *filename,
     for (i = 0; i < fmt_ctx->nb_streams; i++) {
         InputStream *ist = &ifile->streams[i];
         AVStream *stream = fmt_ctx->streams[i];
-        AVCodec *codec;
+        const AVCodec *codec;
 
         ist->st = stream;