[Libav-user] decode_video example pgm files distorted? (v4.0.2 Winbuild)
Chris Bennett
chris.bennett at dreamworks.com
Fri Aug 31 23:56:49 EEST 2018
Hey Strahinja!
Thank you very much for taking the time to help me out.
the pgm snippet you sent looks the same as the decode video example I am
seeing.
Here is the code that I am compiling and running if it helps, hopefully its
not too long. ( I had to add an extern "C" wrapper since my goal is to
build c++ tools with this, and also changed how the example finds the
decoder).
/*
* Copyright (c) 2001 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a
copy
* of this software and associated documentation files (the "Software"), to
deal
* in the Software without restriction, including without limitation the
rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
/**
* @file
* video decoding with libavcodec API example
*
* @example decode_video.c
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat\avformat.h>
}
#define INBUF_SIZE 4096
static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
char *filename)
{
FILE *f;
int i;
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);
fclose(f);
}
static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt,
const char *filename)
{
char buf[1024];
int ret;
ret = avcodec_send_packet(dec_ctx, pkt);
if (ret < 0) {
fprintf(stderr, "Error sending a packet for decoding\n");
exit(1);
}
while (ret >= 0) {
ret = avcodec_receive_frame(dec_ctx, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
return;
else if (ret < 0) {
fprintf(stderr, "Error during decoding\n");
exit(1);
}
printf("saving frame %3d\n", dec_ctx->frame_number);
fflush(stdout);
/* the picture is allocated by the decoder. no need to
free it */
_snprintf(buf, sizeof(buf), "%s-%d.pgm", filename, dec_ctx->frame_number);
pgm_save(frame->data[0], frame->linesize[0],
frame->width, frame->height, buf);
}
}
int main(int argc, char **argv)
{
const char *filename, *outfilename;
const AVCodec *codec;
AVCodecParserContext *parser;
AVCodecContext *c = NULL;
FILE *f;
AVFrame *frame;
uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
uint8_t *data;
size_t data_size;
int ret;
AVPacket *pkt;
if (argc <= 2) {
fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]);
exit(0);
}
filename = argv[1];
outfilename = argv[2];
pkt = av_packet_alloc();
if (!pkt)
exit(1);
/* set end of buffer to 0 (this ensures that no overreading happens for
damaged MPEG streams) */
memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);
//---from test1.cpp
AVFormatContext *pFormatContext = avformat_alloc_context();
if (!pFormatContext) {
fprintf(stderr, "ERROR could not allocate memory for Format Context");
return -1;
}
if (avformat_open_input(&pFormatContext, argv[1], NULL, NULL) != 0) {
fprintf(stderr, "ERROR could not open the file");
return -1;
}
AVCodecParameters *pLocalCodecParameters = NULL;
pLocalCodecParameters = pFormatContext->streams[0]->codecpar;
//-----
/* find the video decoder */
//codec = avcodec_find_decoder(AV_CODEC_ID_MJPEG);
codec = avcodec_find_decoder(pLocalCodecParameters->codec_id);
if (!codec) {
fprintf(stderr, "Codec not found\n");
exit(1);
}
parser = av_parser_init(codec->id);
if (!parser) {
fprintf(stderr, "parser not found\n");
exit(1);
}
c = avcodec_alloc_context3(codec);
if (!c) {
fprintf(stderr, "Could not allocate video codec context\n");
exit(1);
}
/* For some codecs, such as msmpeg4 and mpeg4, width and height
MUST be initialized there because this information is not
available in the bitstream. */
/* open it */
if (avcodec_open2(c, codec, NULL) < 0) {
fprintf(stderr, "Could not open codec\n");
exit(1);
}
f = fopen(filename, "rb");
if (!f) {
fprintf(stderr, "Could not open %s\n", filename);
exit(1);
}
frame = av_frame_alloc();
if (!frame) {
fprintf(stderr, "Could not allocate video frame\n");
exit(1);
}
while (!feof(f)) {
/* read raw data from the input file */
data_size = fread(inbuf, 1, INBUF_SIZE, f);
if (!data_size)
break;
/* use the parser to split the data into frames */
data = inbuf;
while (data_size > 0) {
ret = av_parser_parse2(parser, c, &pkt->data, &pkt->size,
data, data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
if (ret < 0) {
fprintf(stderr, "Error while parsing\n");
exit(1);
}
data += ret;
data_size -= ret;
if (pkt->size)
decode(c, frame, pkt, outfilename);
}
}
/* flush the decoder */
decode(c, frame, NULL, outfilename);
fclose(f);
av_parser_close(parser);
avcodec_free_context(&c);
av_frame_free(&frame);
av_packet_free(&pkt);
return 0;
}
Please let me know if you see anything incorrect with this.
Thanks!
Chris Bennett
Lead Animation Pipeline TD - Television
On Fri, Aug 31, 2018 at 10:48 AM, Strahinja Radman <dr.strashni at gmail.com>
wrote:
> Hi Chris,
>
>
>
> 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)
>
> {
>
> FILE *f;
>
> int i;
>
>
>
> 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);
>
> fclose(f);
>
> }
>
>
>
> The above method should be called with pgm_save(frame->data[0],
> frame->linesize[0], frame->width, frame->height, “name.pgm”);
>
>
>
> Kind regards,
>
> Strahinja
>
>
>
> *From: *Chris Bennett <chris.bennett at dreamworks.com>
> *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)
>
>
>
> Hello All!
>
>
>
> 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.
>
>
>
> Thanks,
>
> Chris Bennett
>
>
>
> _______________________________________________
> Libav-user mailing list
> Libav-user at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/libav-user
>
>
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