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POMPEG-2 video encoding with ffmpeg API: bigger filesize than ffmpeg.exe
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copied!<p>I am trying to encode a video from raw YUV to MPEG-2 using the ffmpeg API. </p> <p>My problem is that the <em>API</em>-generated file is approx. 1.7 times bigger than the equivalent files generated by <em>ffmpeg</em> itself.</p> <p>I use the quantization parameter (via <code>qmin</code> and <code>qmax</code>) instead of the bitrate. </p> <p>The <em>API</em>-version is basically:</p> <pre class="lang-cpp prettyprint-override"><code>//... pCodecCtx->pix_fmt = PIX_FMT_YUV420P; pCodecCtx->qmin = 3; pCodecCtx->qmax = 3; pCodecCtx->time_base.num = 1; pCodecCtx->time_base.den = 30; avcodec_open(pCodecCtx, avcodec_find_encoder(CODEC_ID_MPEG2VIDEO)); //... while(/*...*/) { avcodec_encode_video(pCodecCtx, pOutbuf, outbufSize, pPicture); //.. } //... </code></pre> <p>For <em>ffmpeg</em> itself, I use the command: </p> <pre><code>ffmpeg -s 352x288 -r 30 -i foreman_352x288.yuv -f mpeg2video -vcodec mpeg2video -r 30 -pix_fmt yuv420p -qmin 3 -qmax 3 foreman.m2v </code></pre> <p>Why does the <em>API</em>-generate file achieve a bitrate of 5212 kb/s and the file generated by <em>ffmpeg</em> for the same <code>qp</code> a bitrate of 3047 kb/s?? </p> <p>(Even more puzzling is that the smaller <em>ffmpeg</em> version has a slightly higher PSNR, 40.49 dB vs. 40.02 dB). </p> <p>Are there any other relevant parameters that I missed? Does the <em>ffmpeg</em> actually respect the quantization parameter?</p>

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