avcodec: estimate output bitrate for uncompressed video codecs

Allows to get a more realistic total bitrate (and estimated file size)
in avi_write_header. Previously a static default value of 200k was
assumed.

Adds an internal helper function for bitrate guessing.

Signed-off-by: Tobias Rapp <t.rapp@noa-archive.com>
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>

1 files changed, 21 insertions, 0 deletions

diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 6f7b2e7af7..63a6349703 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -4343,3 +4343,24 @@ int ff_alloc_a53_sei(const AVFrame *frame, size_t prefix_len,
 
     return 0;
 }
+
+int64_t ff_guess_coded_bitrate(AVCodecContext *avctx)
+{
+    AVRational framerate = avctx->framerate;
+    int bits_per_coded_sample = avctx->bits_per_coded_sample;
+    int64_t bitrate;
+
+    if (!(framerate.num && framerate.den))
+        framerate = av_inv_q(avctx->time_base);
+    if (!(framerate.num && framerate.den))
+        return 0;
+
+    if (!bits_per_coded_sample) {
+        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(avctx->pix_fmt);
+        bits_per_coded_sample = av_get_bits_per_pixel(desc);
+    }
+    bitrate = (int64_t)bits_per_coded_sample * avctx->width * avctx->height *
+              framerate.num / framerate.den;
+
+    return bitrate;
+}