lavc: deprecate the omx encoders

They have not been relevant for a long time, and support for this API is
also being dropped from other projects.

Changelog

@@ -5,6 +5,7 @@ version <next>:
 - yasm support dropped, users need to use nasm
 - VVC VAAPI decoder
 - RealVideo 6.0 decoder
+- OpenMAX encoders deprecated
 
 version 7.1:
 - Raw Captions with Time (RCWT) closed caption demuxer

configure

@@ -7110,7 +7110,9 @@ enabled omx_rpi           && { test_code cc OMX_Core.h OMX_IndexConfigBrcmVideoR
                                  test_code cc OMX_Core.h OMX_IndexConfigBrcmVideoRequestIFrame; } ||
                                die "ERROR: OpenMAX IL headers from raspberrypi/firmware not found"; } &&
                              enable omx
-enabled omx               && require_headers OMX_Core.h
+enabled omx               && require_headers OMX_Core.h && \
+    warn "The OpenMAX encoders are deprecated and will be removed in future versions"
+
 enabled openssl           && { { check_pkg_config openssl "openssl >= 3.0.0" openssl/ssl.h OPENSSL_init_ssl &&
                                  { enabled gplv3 || ! enabled gpl || enabled nonfree || die "ERROR: OpenSSL >=3.0.0 requires --enable-version3"; }; } ||
                                { enabled gpl && ! enabled nonfree && die "ERROR: OpenSSL <3.0.0 is incompatible with the gpl"; } ||

libavcodec/omx.c

@@ -648,6 +648,10 @@ static av_cold int omx_encode_init(AVCodecContext *avctx)
     OMX_BUFFERHEADERTYPE *buffer;
     OMX_ERRORTYPE err;
 
+    av_log(avctx, AV_LOG_WARNING,
+           "The %s encoder is deprecated and will be removed in future versions\n",
+           avctx->codec->name);
+
     /* cleanup relies on the mutexes/conditions being initialized first. */
     ret = ff_pthread_init(s, omx_codec_context_offsets);
     if (ret < 0)

libavcodec/version_major.h

@@ -50,4 +50,7 @@
 #define FF_API_QUALITY_FACTOR      (LIBAVCODEC_VERSION_MAJOR < 62)
 #define FF_API_V408_CODECID        (LIBAVCODEC_VERSION_MAJOR < 62)
 
+// reminder to remove the OMX encoder on next major bump
+#define FF_CODEC_OMX               (LIBAVCODEC_VERSION_MAJOR < 62)
+
 #endif /* AVCODEC_VERSION_MAJOR_H */