Zarxrax wrote:Different show compress to different sizes. When you say S1 and S2 I'm guessing you mean two different shows.
Or Season 1, Season 2. 1080p could be coming from Blu-ray, while 720p could be an HDTV capture (or worse, an upscale). The differences there could possibly cause it - the 1080p source would retain more sharpness and clarity when downscaled than something captured at 720p or upscaled. The 1080p could also exhibit ringing artifacts from the Lanczos4Resize you used (generally I can't detect it when downscaling, but then again I'm slightly nearsighted).
Also, are you absolutely sure that both are in YV12? If you're using Lagarith for both then I wouldn't doubt it, but if one or both are HuffYUV, be aware that the standard HuffYUV codec doesn't do YV12 - you need ffdshow's VFW encoder to encode YV12 with HuffYUV (and actually, considering this, it might depend on the settings used for HuffYUV-YV12 - using a different prediction mode and turning the adaptive Huffman tables on or off make quite a bit of difference in filesize; aside from the null frames option, I don't think Lagarith has anything comparable to tweak compression efficiency).