lavc get supported prop fix

There are some calls using just the codec_ctx
parameter, which fail (with the compat with
legacy FFmpeg).

eg. `uv -A Opus -s testcard` (using the old FFmpeg)

Author: MartinPulec

src/audio/capture/sdl_mixer.c

@@ -80,6 +80,7 @@ static void audio_cap_sdl_mixer_probe(struct device_info **available_devices, in
 
 static void sdl_mixer_audio_callback(int chan, void *stream, int len, void *udata)
 {
+        // printf("%d\n", len);
         UNUSED(chan);
         struct state_sdl_mixer_capture *s = udata;
 
@@ -209,7 +210,7 @@ static void * audio_cap_sdl_mixer_init(struct module *parent, const char *cfg)
         }
 
         if( Mix_OpenAudio(SDL_MIXER_SAMPLE_RATE, audio_format,
-                                s->audio.ch_count, 4096 ) == -1 ) {
+                                s->audio.ch_count, 1024 ) == -1 ) {
                 log_msg(LOG_LEVEL_ERROR, MOD_NAME "error initalizing sound: %s\n", Mix_GetError());
                 goto error;
         }

src/libavcodec/lavc_common.c

@@ -380,7 +380,9 @@ avc_get_supported_pix_fmts(const AVCodecContext *ctx, const AVCodec *codec)
 #if LIBAVCODEC_VERSION_INT > AV_VERSION_INT(61, 13, 100)
         return avc_get_supported_config(ctx, codec, AV_CODEC_CONFIG_PIX_FORMAT);
 #else
-        (void) ctx;
+        if (ctx != NULL) {
+          return ctx->codec->pix_fmts;
+        }
         return codec->pix_fmts;
 #endif
 }
@@ -391,7 +393,9 @@ avc_get_supported_sample_fmts(const AVCodecContext *ctx, const AVCodec *codec)
 #if LIBAVCODEC_VERSION_INT > AV_VERSION_INT(61, 13, 100)
         return avc_get_supported_config(ctx, codec, AV_CODEC_CONFIG_SAMPLE_FORMAT);
 #else
-        (void) ctx;
+        if (ctx != NULL) {
+          return ctx->codec->sample_fmts;
+        }
         return codec->sample_fmts;
 #endif
 }
@@ -401,7 +405,9 @@ const int *avc_get_supported_sample_rates(const AVCodecContext *ctx, const AVCod
 #if LIBAVCODEC_VERSION_INT > AV_VERSION_INT(61, 13, 100)
         return avc_get_supported_config(ctx, codec, AV_CODEC_CONFIG_SAMPLE_RATE);
 #else
-        (void) ctx;
+        if (ctx != NULL) {
+          return ctx->codec->supported_samplerates;
+        }
         return codec->supported_samplerates;
 #endif
 }