[FFmpeg-devel] [PATCH] lavc/libopenh264: Drop openh264 runtime version checks

[Kalev Lember]

Years ago, openh264 releases often changed their ABI without changing
the library soname. To avoid running into ABI issues, a version check
was added to lavc libopenh264 code to error out at runtime in case the
build time and runtime openh264 versions don't match.

This should no longer be an issue with newer openh264 releases and we
can drop the runtime version check and rely on upstream doing the right
thing and bump the library soname if the ABI changes, similar to how
other libraries are consumed in ffmpeg.

Almost all major distributions now include openh264 and this means there
are more eyes on ABI changes and issues are discovered and reported
quickly. See e.g. https://github.com/cisco/openh264/issues/3564 where an
ABI issue was quickly discovered and fixed.

Relaxing the check allows downstream distributions to build ffmpeg
against e.g. openh264 2.3.1 and ship an update to ABI-compatible
openh264 2.4.0, without needing to coordinate a lock step update between
ffmpeg and openh264 (which can be difficult if openh264 is distributed
by Cisco and ffmpeg comes from the distro, such as is the case for
Fedora).

Signed-off-by: Kalev Lember <klember at redhat.com>
---
 libavcodec/libopenh264.c    | 15 ---------------
 libavcodec/libopenh264.h    |  2 --
 libavcodec/libopenh264dec.c |  4 ----
 libavcodec/libopenh264enc.c |  4 ----
 4 files changed, 25 deletions(-)

diff --git a/libavcodec/libopenh264.c b/libavcodec/libopenh264.c
index 0f6d28ed88..c80c85ea8b 100644
--- a/libavcodec/libopenh264.c
+++ b/libavcodec/libopenh264.c
@@ -46,18 +46,3 @@ void ff_libopenh264_trace_callback(void *ctx, int level, const char *msg)
     int equiv_ffmpeg_log_level = libopenh264_to_ffmpeg_log_level(level);
     av_log(ctx, equiv_ffmpeg_log_level, "%s\n", msg);
 }
-
-int ff_libopenh264_check_version(void *logctx)
-{
-    // Mingw GCC < 4.7 on x86_32 uses an incorrect/buggy ABI for the WelsGetCodecVersion
-    // function (for functions returning larger structs), thus skip the check in those
-    // configurations.
-#if !defined(_WIN32) || !defined(__GNUC__) || !ARCH_X86_32 || AV_GCC_VERSION_AT_LEAST(4, 7)
-    OpenH264Version libver = WelsGetCodecVersion();
-    if (memcmp(&libver, &g_stCodecVersion, sizeof(libver))) {
-        av_log(logctx, AV_LOG_ERROR, "Incorrect library version loaded\n");
-        return AVERROR(EINVAL);
-    }
-#endif
-    return 0;
-}
diff --git a/libavcodec/libopenh264.h b/libavcodec/libopenh264.h
index dbb9c5d429..0b462d6fdc 100644
--- a/libavcodec/libopenh264.h
+++ b/libavcodec/libopenh264.h
@@ -34,6 +34,4 @@
 
 void ff_libopenh264_trace_callback(void *ctx, int level, const char *msg);
 
-int ff_libopenh264_check_version(void *logctx);
-
 #endif /* AVCODEC_LIBOPENH264_H */
diff --git a/libavcodec/libopenh264dec.c b/libavcodec/libopenh264dec.c
index 7d650ae03e..b6a9bba2dc 100644
--- a/libavcodec/libopenh264dec.c
+++ b/libavcodec/libopenh264dec.c
@@ -52,13 +52,9 @@ static av_cold int svc_decode_init(AVCodecContext *avctx)
 {
     SVCContext *s = avctx->priv_data;
     SDecodingParam param = { 0 };
-    int err;
     int log_level;
     WelsTraceCallback callback_function;
 
-    if ((err = ff_libopenh264_check_version(avctx)) < 0)
-        return AVERROR_DECODER_NOT_FOUND;
-
     if (WelsCreateDecoder(&s->decoder)) {
         av_log(avctx, AV_LOG_ERROR, "Unable to create decoder\n");
         return AVERROR_UNKNOWN;
diff --git a/libavcodec/libopenh264enc.c b/libavcodec/libopenh264enc.c
index f518d0894e..6f231d22b2 100644
--- a/libavcodec/libopenh264enc.c
+++ b/libavcodec/libopenh264enc.c
@@ -110,14 +110,10 @@ static av_cold int svc_encode_init(AVCodecContext *avctx)
 {
     SVCContext *s = avctx->priv_data;
     SEncParamExt param = { 0 };
-    int err;
     int log_level;
     WelsTraceCallback callback_function;
     AVCPBProperties *props;
 
-    if ((err = ff_libopenh264_check_version(avctx)) < 0)
-        return AVERROR_ENCODER_NOT_FOUND;
-
     if (WelsCreateSVCEncoder(&s->encoder)) {
         av_log(avctx, AV_LOG_ERROR, "Unable to create encoder\n");
         return AVERROR_UNKNOWN;
-- 
2.43.0