[FFmpeg-devel] avformat option strange behaviour

[Clément Bœsch]

Hi,

It seems the format option parsing is broken in FFmpeg, but I can't figure
out why. I still didn't do a git bisect to track down the issue, but
someone may have a hint about this.

I attached a dummy patch to add an option to a random format, and tried to
use it. Unfortunately, the -foobar bla never set the option in the context
struct; the option is well recognized and parsed (it fills the options
dict), but that dict may not be used. I'm almost certain it's a bug since
applying the exact same patch works with libav HEAD.

-- 
Clément B.
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diff --git a/libavformat/mxfenc.c b/libavformat/mxfenc.c
index b84504c..913a605 100644
--- a/libavformat/mxfenc.c
+++ b/libavformat/mxfenc.c
@@ -35,6 +35,7 @@
 #include <math.h>
 #include <time.h>
 
+#include "libavutil/opt.h"
 #include "libavutil/random_seed.h"
 #include "libavcodec/bytestream.h"
 #include "audiointerleave.h"
@@ -171,6 +172,7 @@ static const MXFContainerEssenceEntry mxf_essence_container_uls[] = {
 };
 
 typedef struct MXFContext {
+    AVClass *av_class;
     int64_t footer_partition_offset;
     int essence_container_count;
     AVRational time_base;
@@ -192,6 +194,7 @@ typedef struct MXFContext {
     uint64_t body_offset;
     uint32_t instance_number;
     uint8_t umid[16];        ///< unique material identifier
+    char *foobar;
 } MXFContext;
 
 static const uint8_t uuid_base[]            = { 0xAD,0xAB,0x44,0x24,0x2f,0x25,0x4d,0xc7,0x92,0xff,0x29,0xbd };
@@ -1411,6 +1414,8 @@ static int mxf_write_header(AVFormatContext *s)
     AVDictionaryEntry *t;
     int64_t timestamp = 0;
 
+    av_log(0,0,"foobar=%s\n", mxf->foobar);
+
     if (!s->nb_streams)
         return -1;
 
@@ -1889,6 +1894,16 @@ static int mxf_interleave(AVFormatContext *s, AVPacket *out, AVPacket *pkt, int
                                mxf_interleave_get_packet, mxf_compare_timestamps);
 }
 
+static const AVClass class = {
+    .class_name = "mxf",
+    .item_name  = av_default_item_name,
+    .version    = LIBAVUTIL_VERSION_INT,
+    .option     = (const AVOption[]){
+        {"foobar", "", offsetof(MXFContext, foobar), FF_OPT_TYPE_STRING, {.str=NULL}, CHAR_MIN, CHAR_MAX, AV_OPT_FLAG_ENCODING_PARAM},
+        {NULL}
+    },
+};
+
 AVOutputFormat ff_mxf_muxer = {
     .name              = "mxf",
     .long_name         = NULL_IF_CONFIG_SMALL("Material eXchange Format"),
@@ -1902,6 +1917,7 @@ AVOutputFormat ff_mxf_muxer = {
     .write_trailer     = mxf_write_footer,
     .flags             = AVFMT_NOTIMESTAMPS,
     .interleave_packet = mxf_interleave,
+    .priv_class        = &class,
 };
 
 AVOutputFormat ff_mxf_d10_muxer = {
@@ -1916,4 +1932,5 @@ AVOutputFormat ff_mxf_d10_muxer = {
     .write_trailer     = mxf_write_footer,
     .flags             = AVFMT_NOTIMESTAMPS,
     .interleave_packet = mxf_interleave,
+    .priv_class        = &class,
 };
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