Convert YUV frames into RGBA frames with FFMPEG - ffmpeg

Question

I would like to develop an application which would be able to convert YUV frames into RGBA frames using the ffmpeg library.
I have begun writing this code:
void Decode::video_encode_example(const char *filename, int codec_id)
{
AVCodec *codec;
AVCodecContext *c= NULL;
int i, ret, x, y, got_output;
FILE *f;
AVFrame *frame;
AVPacket pkt;
uint8_t endcode[] = { 0, 0, 1, 0xb7 };
printf("Encode video file %s\n", filename);
/* find the mpeg1 video encoder */
codec = avcodec_find_encoder((enum AVCodecID)codec_id);
if (!codec) {
fprintf(stderr, "Codec not found\n");
exit(1);
}
c = avcodec_alloc_context3(codec);
if (!c) {
fprintf(stderr, "Could not allocate video codec context\n");
exit(2);
}
/* put sample parameters */
c->bit_rate = 400000;
/* resolution must be a multiple of two */
c->width = 352; // Avant c'était du 352x288
c->height = 288;
/* frames per second */
c->time_base = (AVRational){1,25};
/* emit one intra frame every ten frames
* check frame pict_type before passing frame
* to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
* then gop_size is ignored and the output of encoder
* will always be I frame irrespective to gop_size
*/
c->gop_size = 10;
c->max_b_frames = 1;
printf("Avant\n");
c->pix_fmt = PIX_FMT_RGBA;// Avant c'était AV_PIX_FMT_YUV420P
printf("Après\n");
if (codec_id == AV_CODEC_ID_H264)
av_opt_set(c->priv_data, "preset", "slow", 0);
/* open it */
if (avcodec_open2(c, codec, NULL) < 0) {
fprintf(stderr, "Could not open codec\n");
exit(3);
}
f = fopen(filename, "wb");
if (!f) {
fprintf(stderr, "Could not open %s\n", filename);
exit(4);
}
frame = avcodec_alloc_frame();// Dans une version plus récente c'est av_frame_alloc
if (!frame) {
fprintf(stderr, "Could not allocate video frame\n");
exit(5);
}
frame->format = c->pix_fmt;
frame->width = c->width;
frame->height = c->height;
However, each time I run this application, the following error appears in my Linux terminal:
[mpeg2video # 0x10c7040] Specified pix_fmt is not supported
Could you help me please ?

Answer 1

I'm not sure how you believe your code is relevant to your question; your question suggests you'd like to do a pixel format conversion from YUV to RGB, for which you could e.g. use ffmpeg's libswscale. However, your code is creating a MPEG-1/2 encoder object and tries to encode RGB input data into MPEG-1/2. This is not possible, ffmpeg's MPEG-1/2 encoders only support YUV420P. I'm not quite sure what to recommend other than to figure out whether you want to encode MPEG-1/2 video, in which case your input should be YUV420P, not RGBA, or whether you want to do pixel format conversion, in which case you should use libswscale...