[FFmpeg-devel] [PATCH 4/5] ffmpeg: keep bitdepth where possible

[Christophe Gisquet]

Thanks to av_get_pix_fmt_loss, we can determine more precisely if a
conversion will incur some kind of loss. If this loss doesn't modify
in particular bitdepth, the input bitdepth can be reused for the
output.
---
 ffmpeg.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/ffmpeg.c b/ffmpeg.c
index fa907b4..2bfa047 100644
--- a/ffmpeg.c
+++ b/ffmpeg.c
@@ -2774,6 +2774,15 @@ static int transcode_init(void)
                     enc_ctx->bits_per_raw_sample = frame_bits_per_raw_sample;
                 }
 
+                if (!(av_get_pix_fmt_loss(enc_ctx->pix_fmt, dec_ctx->pix_fmt, 0)
+                      & (FF_LOSS_DEPTH|FF_LOSS_COLORSPACE|FF_LOSS_CHROMA))) {
+                    const AVPixFmtDescriptor *pix1 = av_pix_fmt_desc_get(enc_ctx->pix_fmt);
+                    const AVPixFmtDescriptor *pix2 = av_pix_fmt_desc_get(dec_ctx->pix_fmt);
+                    if (pix1 && pix2 &&
+                        av_get_bits_per_pixel(pix1) == av_get_bits_per_pixel(pix2))
+                        enc_ctx->bits_per_raw_sample = dec_ctx->bits_per_raw_sample;
+                }
+
                 if (ost->forced_keyframes) {
                     if (!strncmp(ost->forced_keyframes, "expr:", 5)) {
                         ret = av_expr_parse(&ost->forced_keyframes_pexpr, ost->forced_keyframes+5,
-- 
1.9.2.msysgit.0