diff --git a/libavcodec/avcodec.c b/libavcodec/avcodec.c
index 3088d2ff3f..93383dc9fb 100644
--- a/libavcodec/avcodec.c
+++ b/libavcodec/avcodec.c
@@ -607,6 +607,7 @@ void avcodec_string(char *buf, int buf_size, AVCodecContext *enc, int encode)
     int new_line = 0;
     AVRational display_aspect_ratio;
     const char *separator = enc->dump_separator ? (const char *)enc->dump_separator : ", ";
+    const char *str;
 
     if (!buf || buf_size <= 0)
         return;
@@ -642,14 +643,14 @@ void avcodec_string(char *buf, int buf_size, AVCodecContext *enc, int encode)
             av_strlcat(buf, separator, buf_size);
 
             snprintf(buf + strlen(buf), buf_size - strlen(buf),
-                 "%s", enc->pix_fmt == AV_PIX_FMT_NONE ? "none" :
-                     av_get_pix_fmt_name(enc->pix_fmt));
+                     "%s", enc->pix_fmt == AV_PIX_FMT_NONE ? "none" :
+                     av_x_if_null(av_get_pix_fmt_name(enc->pix_fmt), "unknown"));
             if (enc->bits_per_raw_sample && enc->pix_fmt != AV_PIX_FMT_NONE &&
                 enc->bits_per_raw_sample < av_pix_fmt_desc_get(enc->pix_fmt)->comp[0].depth)
                 av_strlcatf(detail, sizeof(detail), "%d bpc, ", enc->bits_per_raw_sample);
-            if (enc->color_range != AVCOL_RANGE_UNSPECIFIED)
-                av_strlcatf(detail, sizeof(detail), "%s, ",
-                            av_color_range_name(enc->color_range));
+            if (enc->color_range != AVCOL_RANGE_UNSPECIFIED &&
+                (str = av_color_range_name(enc->color_range)))
+                av_strlcatf(detail, sizeof(detail), "%s, ", str);
 
             if (enc->colorspace != AVCOL_SPC_UNSPECIFIED ||
                 enc->color_primaries != AVCOL_PRI_UNSPECIFIED ||
@@ -658,12 +659,11 @@ void avcodec_string(char *buf, int buf_size, AVCodecContext *enc, int encode)
                     enc->colorspace != (int)enc->color_trc) {
                     new_line = 1;
                     av_strlcatf(detail, sizeof(detail), "%s/%s/%s, ",
-                                av_color_space_name(enc->colorspace),
-                                av_color_primaries_name(enc->color_primaries),
-                                av_color_transfer_name(enc->color_trc));
-                } else
-                    av_strlcatf(detail, sizeof(detail), "%s, ",
-                                av_get_colorspace_name(enc->colorspace));
+                                av_x_if_null(av_color_space_name(enc->colorspace), "unknown"),
+                                av_x_if_null(av_color_primaries_name(enc->color_primaries), "unknown"),
+                                av_x_if_null(av_color_transfer_name(enc->color_trc), "unkown"));
+                 } else if (str = av_get_colorspace_name(enc->colorspace))
+                       av_strlcatf(detail, sizeof(detail), "%s, ", str);
             }
 
             if (enc->field_order != AV_FIELD_UNKNOWN) {
@@ -681,9 +681,9 @@ void avcodec_string(char *buf, int buf_size, AVCodecContext *enc, int encode)
             }
 
             if (av_log_get_level() >= AV_LOG_VERBOSE &&
-                enc->chroma_sample_location != AVCHROMA_LOC_UNSPECIFIED)
-                av_strlcatf(detail, sizeof(detail), "%s, ",
-                            av_chroma_location_name(enc->chroma_sample_location));
+                enc->chroma_sample_location != AVCHROMA_LOC_UNSPECIFIED &&
+                (str = av_chroma_location_name(enc->chroma_sample_location)))
+                av_strlcatf(detail, sizeof(detail), "%s, ", str);
 
             if (strlen(detail) > 1) {
                 detail[strlen(detail) - 2] = 0;
@@ -741,9 +741,10 @@ void avcodec_string(char *buf, int buf_size, AVCodecContext *enc, int encode)
                      "%d Hz, ", enc->sample_rate);
         }
         av_get_channel_layout_string(buf + strlen(buf), buf_size - strlen(buf), enc->channels, enc->channel_layout);
-        if (enc->sample_fmt != AV_SAMPLE_FMT_NONE) {
+        if (enc->sample_fmt != AV_SAMPLE_FMT_NONE &&
+            (str = av_get_sample_fmt_name(enc->sample_fmt))) {
             snprintf(buf + strlen(buf), buf_size - strlen(buf),
-                     ", %s", av_get_sample_fmt_name(enc->sample_fmt));
+                     ", %s", str);
         }
         if (   enc->bits_per_raw_sample > 0
             && enc->bits_per_raw_sample != av_get_bytes_per_sample(enc->sample_fmt) * 8)
