[PATCH 1/7] Implement av_get_codec_tag_string() and use it in ffprobe.

[Stefano Sabatini]

---
 ffprobe.c            |   14 +++-----------
 libavcodec/avcodec.h |    9 +++++++++
 libavcodec/utils.c   |   31 +++++++++++++++++++++++++++++++
 3 files changed, 43 insertions(+), 11 deletions(-)

diff --git a/ffprobe.c b/ffprobe.c
index 7cb6167..4be5d0f 100644
--- a/ffprobe.c
+++ b/ffprobe.c
@@ -120,7 +120,6 @@ static void show_stream(AVFormatContext *fmt_ctx, int stream_idx)
     AVCodec *dec;
     char val_str[128];
     AVMetadataTag *tag = NULL;
-    char a, b, c, d;
     AVRational display_aspect_ratio;
 
     printf("[STREAM]\n");
@@ -139,16 +138,9 @@ static void show_stream(AVFormatContext *fmt_ctx, int stream_idx)
         printf("codec_time_base=%d/%d\n", dec_ctx->time_base.num, dec_ctx->time_base.den);
 
         /* print AVI/FourCC tag */
-        a = dec_ctx->codec_tag     & 0xff;
-        b = dec_ctx->codec_tag>>8  & 0xff;
-        c = dec_ctx->codec_tag>>16 & 0xff;
-        d = dec_ctx->codec_tag>>24 & 0xff;
-        printf("codec_tag_string=");
-        if (isprint(a)) printf("%c", a); else printf("[%d]", a);
-        if (isprint(b)) printf("%c", b); else printf("[%d]", b);
-        if (isprint(c)) printf("%c", c); else printf("[%d]", c);
-        if (isprint(d)) printf("%c", d); else printf("[%d]", d);
-        printf("\ncodec_tag=0x%04x\n", dec_ctx->codec_tag);
+        av_get_codec_tag_string(val_str, sizeof(val_str), dec_ctx->codec_tag);
+        printf("codec_tag_string=%s\n", val_str);
+        printf("codec_tag=0x%04x\n", dec_ctx->codec_tag);
 
         switch (dec_ctx->codec_type) {
         case AVMEDIA_TYPE_VIDEO:
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index a07e774..0150ade 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -3093,6 +3093,15 @@ attribute_deprecated enum PixelFormat avcodec_get_pix_fmt(const char* name);
  */
 unsigned int avcodec_pix_fmt_to_codec_tag(enum PixelFormat pix_fmt);
 
+/**
+ * Puts a string representing the codec tag codec_tag in buf.
+ *
+ * @param buf_size size in bytes of buf
+ * @return the length of the string that would have been generated if
+ * enough space had been available, excluding the trailing null
+ */
+size_t av_get_codec_tag_string(char *buf, size_t buf_size, unsigned int codec_tag);
+
 #define FF_LOSS_RESOLUTION  0x0001 /**< loss due to resolution change */
 #define FF_LOSS_DEPTH       0x0002 /**< loss due to color depth change */
 #define FF_LOSS_COLORSPACE  0x0004 /**< loss due to color space conversion */
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 60f52ac..e86c021 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -802,6 +802,21 @@ static int get_bit_rate(AVCodecContext *ctx)
     return bit_rate;
 }
 
+size_t av_get_codec_tag_string(char *buf, size_t buf_size, unsigned int codec_tag)
+{
+    int i, len, ret = 0;
+
+    for (i = 0; i < 4; i++) {
+        len = snprintf(buf, buf_size,
+                       isprint(codec_tag&0xFF) ? "%c" : "[%d]", codec_tag&0xFF);
+        buf      += len;
+        buf_size  = buf_size > len ? buf_size - len : 0;
+        ret      += len;
+        codec_tag>>=8;
+    }
+    return ret;
+}
+
 void avcodec_string(char *buf, int buf_size, AVCodecContext *enc, int encode)
 {
     const char *codec_name;
@@ -1306,3 +1321,19 @@ unsigned int ff_toupper4(unsigned int x)
             + (toupper((x>>16)&0xFF)<<16)
             + (toupper((x>>24)&0xFF)<<24);
 }
+
+#ifdef TEST
+
+#undef printf
+
+int main(void)
+{
+    char buf[16];
+    for (int i = 0; i < sizeof(buf); i++) {
+        size_t ret = av_get_codec_tag_string(buf, i, 0x80b3459);
+        printf("i:%d ret:%u tag:%s\n", i, ret, buf);
+    }
+    return 0;
+}
+
+#endif
-- 
1.7.1


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