[Libav-user] decode_video example pgm files distorted? (v4.0.2 Winbuild)
dr.strashni at gmail.com
Fri Aug 31 20:48:22 EEST 2018
To me that looks like you wrote some wrong data inside the picture and it looks skewed. Some indexes could be wrong.
void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, const char *filename)
f = fopen(filename, "w");
fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
for (i = 0; i < ysize; i++)
fwrite(buf + i * wrap, 1, xsize, f);
The above method should be called with pgm_save(frame->data, frame->linesize, frame->width, frame->height, “name.pgm”);
From: Chris Bennett
Sent: 31 August 2018 19:41
To: libav-user at ffmpeg.org
Subject: [Libav-user] decode_video example pgm files distorted? (v4.0.2 Winbuild)
My apologies if this is a rookie question as I am just now learning the innards of ffmpeg, but I am reaching out hoping someone may have had the same issue as myself or has any advice.
I cloned 4.0.2 and compiled the libraries (MS VS 2013 x64) without issue.
I decided to try the examples as a learning opportunity, choosing decode_video. I ended up with this result: https://drive.google.com/file/d/1DPu1EaM7i5J3LFaaGmZNO4Hoi_QzVcKM/view?usp=sharing
At the top and bottom of the image there is is wavy distortion. I am not sure what is causing it.
The source file is a quicktime of a Motion JPEG video.
I had also compiled the exe as well and ran this command
ffmpeg.exe -ss 0.5 -i my_quicktime.mov -t 1 -s 480x300 -f image2 C:/frame-%03d.jpg
and those images turned out just fine (I am sure this probably runs some completely different underlying code but I just wanted to make sure what I compiled was capable of a successful result)
I figure I am doing something incorrectly but I do not know where else to look. If anyone has any advice on what to tinker with, I would greatly appreciate it.
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