[FFmpeg-devel] [PATCH 1/2] avformat/mvdec: read frame rate from data stream

[FFmpeg-devel] [PATCH 1/2] avformat/mvdec: read frame rate from data stream

[John-Paul Stewart]

Prior to this patch, for version 2 of the file format the frame rate was
hard-coded at 15 fps.  This uses the 64-bit floating-point value from
the data stream, similar to what is already done for version 3 of the
file format (around line 206).

Signed-off-by: John-Paul Stewart <jpstewart@personalprojects.net>
---
 libavformat/mvdec.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/libavformat/mvdec.c b/libavformat/mvdec.c
index 5d184f20a4..a5c5b205a6 100644
--- a/libavformat/mvdec.c
+++ b/libavformat/mvdec.c
@@ -26,6 +26,7 @@
 
 #include "libavutil/channel_layout.h"
 #include "libavutil/eval.h"
+#include "libavutil/intfloat.h"
 #include "libavutil/intreadwrite.h"
 #include "libavutil/rational.h"
 
@@ -300,8 +301,9 @@ static int mv_read_header(AVFormatContext *avctx)
         uint64_t timestamp;
         int v;
         uint32_t bytes_per_sample;
+        AVRational fps;
 
-        avio_skip(pb, 22);
+        avio_skip(pb, 10);
 
         /* allocate audio track first to prevent unnecessary seeking
          * (audio packet always precede video packet for a given frame) */
@@ -312,9 +314,11 @@ static int mv_read_header(AVFormatContext *avctx)
         vst = avformat_new_stream(avctx, NULL);
         if (!vst)
             return AVERROR(ENOMEM);
-        avpriv_set_pts_info(vst, 64, 1, 15);
+        fps = av_d2q(av_int2double(avio_rb64(pb)), INT_MAX);
+        avpriv_set_pts_info(vst, 64, fps.den, fps.num);
+        avio_skip(pb, 4);
         vst->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
-        vst->avg_frame_rate    = av_inv_q(vst->time_base);
+        vst->avg_frame_rate = fps;
         vst->nb_frames         = avio_rb32(pb);
         v = avio_rb32(pb);
         switch (v) {
-- 
2.34.1

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[FFmpeg-devel] [PATCH 2/2] avformat/mvdec: explicitly set duration

[John-Paul Stewart]

Resolves a warning that duration is being innaccurately estimated based
on bitrate.

Signed-off-by: John-Paul Stewart <jpstewart@personalprojects.net>
---
 libavformat/mvdec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavformat/mvdec.c b/libavformat/mvdec.c
index a5c5b205a6..1a5012e507 100644
--- a/libavformat/mvdec.c
+++ b/libavformat/mvdec.c
@@ -319,7 +319,7 @@ static int mv_read_header(AVFormatContext *avctx)
         avio_skip(pb, 4);
         vst->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
         vst->avg_frame_rate = fps;
-        vst->nb_frames         = avio_rb32(pb);
+        vst->duration = vst->nb_frames = avio_rb32(pb);
         v = avio_rb32(pb);
         switch (v) {
         case 1:
-- 
2.34.1

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Re: [FFmpeg-devel] [PATCH 2/2] avformat/mvdec: explicitly set duration

[Peter Ross]

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On Sat, Dec 18, 2021 at 03:46:28PM -0500, John-Paul Stewart wrote:
> Resolves a warning that duration is being innaccurately estimated based
> on bitrate.
> 
> Signed-off-by: John-Paul Stewart <jpstewart@personalprojects.net>
> ---
>  libavformat/mvdec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavformat/mvdec.c b/libavformat/mvdec.c
> index a5c5b205a6..1a5012e507 100644
> --- a/libavformat/mvdec.c
> +++ b/libavformat/mvdec.c
> @@ -319,7 +319,7 @@ static int mv_read_header(AVFormatContext *avctx)
>          avio_skip(pb, 4);
>          vst->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
>          vst->avg_frame_rate = fps;
> -        vst->nb_frames         = avio_rb32(pb);
> +        vst->duration = vst->nb_frames = avio_rb32(pb);
>          v = avio_rb32(pb);
>          switch (v) {
>          case 1:

both patches look good, and do not break tests.
i will apply in a couple of days.

-- Peter
(A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)

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