[FFmpeg-devel] [PATCH] lavc/libopenh264: Check for noopenh264

[Akihiko Odaki <akihiko.odaki@gmail.com>]

noopenh264 is a "fake implementation of the OpenH264 library we can link
from regardless of the actual library being available":
https://gitlab.com/freedesktop-sdk/noopenh264

A distributor may wish to link against openh264/noopenh264 and let
the decoder and encoder work only if the actual library is available.

On the other hand, an application may want to know if the decoder or
encoder is available beforehand so that it can determine what format to
download for decoding, or what format to advertise for the peer
receiving the encoded video.

Check the availability of the actual library at runtime initialization
and do not expose the encoder and decoder if they are not available.

Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
---
 libavcodec/codec_internal.h |  2 ++
 libavcodec/libopenh264dec.c | 36 +++++++++++++++++++++++------------
 libavcodec/libopenh264enc.c | 46 ++++++++++++++++++++++++++++-----------------
 libavcodec/tests/avcodec.c  |  2 ++
 4 files changed, 57 insertions(+), 29 deletions(-)

diff --git a/libavcodec/codec_internal.h b/libavcodec/codec_internal.h
index 130a7dc3cd..635af644fa 100644
--- a/libavcodec/codec_internal.h
+++ b/libavcodec/codec_internal.h
@@ -122,6 +122,8 @@ enum FFCodecType {
     /* The codec is an encoder using the receive_packet callback;
      * audio and video codecs only. */
     FF_CODEC_CB_TYPE_RECEIVE_PACKET,
+    /* The codec is not available. */
+    FF_CODEC_CB_TYPE_NONE,
 };
 
 typedef struct FFCodec {
diff --git a/libavcodec/libopenh264dec.c b/libavcodec/libopenh264dec.c
index b6a9bba2dc..f5544142aa 100644
--- a/libavcodec/libopenh264dec.c
+++ b/libavcodec/libopenh264dec.c
@@ -48,6 +48,17 @@ static av_cold int svc_decode_close(AVCodecContext *avctx)
     return 0;
 }
 
+static av_cold void svc_decode_init_static_data(FFCodec *codec)
+{
+    ISVCDecoder *decoder;
+
+    if (WelsCreateDecoder(&decoder)) {
+        codec->cb_type = FF_CODEC_CB_TYPE_NONE;
+    } else {
+        WelsDestroyDecoder(decoder);
+    }
+}
+
 static av_cold int svc_decode_init(AVCodecContext *avctx)
 {
     SVCContext *s = avctx->priv_data;
@@ -153,18 +164,19 @@ static int svc_decode_frame(AVCodecContext *avctx, AVFrame *avframe,
     return avpkt->size;
 }
 
-const FFCodec ff_libopenh264_decoder = {
-    .p.name         = "libopenh264",
+FFCodec ff_libopenh264_decoder = {
+    .p.name           = "libopenh264",
     CODEC_LONG_NAME("OpenH264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10"),
-    .p.type         = AVMEDIA_TYPE_VIDEO,
-    .p.id           = AV_CODEC_ID_H264,
-    .priv_data_size = sizeof(SVCContext),
-    .init           = svc_decode_init,
+    .p.type           = AVMEDIA_TYPE_VIDEO,
+    .p.id             = AV_CODEC_ID_H264,
+    .priv_data_size   = sizeof(SVCContext),
+    .init_static_data = svc_decode_init_static_data,
+    .init             = svc_decode_init,
     FF_CODEC_DECODE_CB(svc_decode_frame),
-    .close          = svc_decode_close,
-    .p.capabilities = AV_CODEC_CAP_DELAY | AV_CODEC_CAP_DR1,
-    .caps_internal  = FF_CODEC_CAP_SETS_PKT_DTS |
-                      FF_CODEC_CAP_INIT_CLEANUP,
-    .bsfs           = "h264_mp4toannexb",
-    .p.wrapper_name = "libopenh264",
+    .close            = svc_decode_close,
+    .p.capabilities   = AV_CODEC_CAP_DELAY | AV_CODEC_CAP_DR1,
+    .caps_internal    = FF_CODEC_CAP_SETS_PKT_DTS |
+                        FF_CODEC_CAP_INIT_CLEANUP,
+    .bsfs             = "h264_mp4toannexb",
+    .p.wrapper_name   = "libopenh264",
 };
diff --git a/libavcodec/libopenh264enc.c b/libavcodec/libopenh264enc.c
index 6f231d22b2..1963f2cf5c 100644
--- a/libavcodec/libopenh264enc.c
+++ b/libavcodec/libopenh264enc.c
@@ -106,6 +106,17 @@ static av_cold int svc_encode_close(AVCodecContext *avctx)
     return 0;
 }
 
+static av_cold void svc_encode_init_static_data(FFCodec *codec)
+{
+    ISVCEncoder *encoder;
+
+    if (WelsCreateSVCEncoder(&encoder)) {
+        codec->cb_type = FF_CODEC_CB_TYPE_NONE;
+    } else {
+        WelsDestroySVCEncoder(encoder);
+    }
+}
+
 static av_cold int svc_encode_init(AVCodecContext *avctx)
 {
     SVCContext *s = avctx->priv_data;
@@ -429,23 +440,24 @@ static const FFCodecDefault svc_enc_defaults[] = {
     { NULL },
 };
 
-const FFCodec ff_libopenh264_encoder = {
-    .p.name         = "libopenh264",
+FFCodec ff_libopenh264_encoder = {
+    .p.name           = "libopenh264",
     CODEC_LONG_NAME("OpenH264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10"),
-    .p.type         = AVMEDIA_TYPE_VIDEO,
-    .p.id           = AV_CODEC_ID_H264,
-    .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_OTHER_THREADS |
-                      AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE,
-    .priv_data_size = sizeof(SVCContext),
-    .init           = svc_encode_init,
+    .p.type           = AVMEDIA_TYPE_VIDEO,
+    .p.id             = AV_CODEC_ID_H264,
+    .p.capabilities   = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_OTHER_THREADS |
+                        AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE,
+    .priv_data_size   = sizeof(SVCContext),
+    .init_static_data = svc_encode_init_static_data,
+    .init             = svc_encode_init,
     FF_CODEC_ENCODE_CB(svc_encode_frame),
-    .close          = svc_encode_close,
-    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP |
-                      FF_CODEC_CAP_AUTO_THREADS,
-    .p.pix_fmts     = (const enum AVPixelFormat[]){ AV_PIX_FMT_YUV420P,
-                                                    AV_PIX_FMT_YUVJ420P,
-                                                    AV_PIX_FMT_NONE },
-    .defaults       = svc_enc_defaults,
-    .p.priv_class   = &class,
-    .p.wrapper_name = "libopenh264",
+    .close            = svc_encode_close,
+    .caps_internal    = FF_CODEC_CAP_INIT_CLEANUP |
+                        FF_CODEC_CAP_AUTO_THREADS,
+    .p.pix_fmts       = (const enum AVPixelFormat[]){ AV_PIX_FMT_YUV420P,
+                                                      AV_PIX_FMT_YUVJ420P,
+                                                      AV_PIX_FMT_NONE },
+    .defaults         = svc_enc_defaults,
+    .p.priv_class     = &class,
+    .p.wrapper_name   = "libopenh264",
 };
diff --git a/libavcodec/tests/avcodec.c b/libavcodec/tests/avcodec.c
index 08ca507bf0..0e2ecccbf9 100644
--- a/libavcodec/tests/avcodec.c
+++ b/libavcodec/tests/avcodec.c
@@ -112,6 +112,8 @@ int main(void){
         case FF_CODEC_CB_TYPE_RECEIVE_PACKET:
             is_encoder = 1;
             break;
+        case FF_CODEC_CB_TYPE_NONE:
+            continue;
         default:
             ERR("Codec %s has unknown cb_type\n");
             continue;

---
base-commit: 81c2557691b12ceb79b3ba92aa496f2301ab4d18
change-id: 20240210-noopenh264-650461efbc33

Best regards,
-- 
Akihiko Odaki <akihiko.odaki@gmail.com>

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