libavformat: Add a utility function for adding parameter change side data

Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/internal.h

@@ -299,4 +299,12 @@ int64_t ff_gen_search(AVFormatContext *s, int stream_index,
 void avpriv_set_pts_info(AVStream *s, int pts_wrap_bits,
                          unsigned int pts_num, unsigned int pts_den);
 
+/**
+ * Add side data to a packet for changing parameters to the given values.
+ * Parameters set to 0 aren't included in the change.
+ */
+int ff_add_param_change(AVPacket *pkt, int32_t channels,
+                        uint64_t channel_layout, int32_t sample_rate,
+                        int32_t width, int32_t height);
+
 #endif /* AVFORMAT_INTERNAL_H */

libavformat/utils.c

@@ -25,6 +25,7 @@
 #include "avio_internal.h"
 #include "internal.h"
 #include "libavcodec/internal.h"
+#include "libavcodec/bytestream.h"
 #include "libavutil/opt.h"
 #include "libavutil/dict.h"
 #include "libavutil/pixdesc.h"
@@ -4017,3 +4018,45 @@ int avformat_network_deinit(void)
 #endif
     return 0;
 }
+
+int ff_add_param_change(AVPacket *pkt, int32_t channels,
+                        uint64_t channel_layout, int32_t sample_rate,
+                        int32_t width, int32_t height)
+{
+    uint32_t flags = 0;
+    int size = 4;
+    uint8_t *data;
+    if (!pkt)
+        return AVERROR(EINVAL);
+    if (channels) {
+        size += 4;
+        flags |= AV_SIDE_DATA_PARAM_CHANGE_CHANNEL_COUNT;
+    }
+    if (channel_layout) {
+        size += 8;
+        flags |= AV_SIDE_DATA_PARAM_CHANGE_CHANNEL_LAYOUT;
+    }
+    if (sample_rate) {
+        size += 4;
+        flags |= AV_SIDE_DATA_PARAM_CHANGE_SAMPLE_RATE;
+    }
+    if (width || height) {
+        size += 8;
+        flags |= AV_SIDE_DATA_PARAM_CHANGE_DIMENSIONS;
+    }
+    data = av_packet_new_side_data(pkt, AV_PKT_DATA_PARAM_CHANGE, size);
+    if (!data)
+        return AVERROR(ENOMEM);
+    bytestream_put_le32(&data, flags);
+    if (channels)
+        bytestream_put_le32(&data, channels);
+    if (channel_layout)
+        bytestream_put_le64(&data, channel_layout);
+    if (sample_rate)
+        bytestream_put_le32(&data, sample_rate);
+    if (width || height) {
+        bytestream_put_le32(&data, width);
+        bytestream_put_le32(&data, height);
+    }
+    return 0;
+}