Video compression may only cause issues at the edges due to chroma subsampling, in which case bleeding chroma to transparent pixels would help. All other cases would be errors in the pipeline, such as incorrect gamma handling, wrong supersampling implementation, or mixing up whether content is premultiplied or not.
Also premultiplication is just a way to cache the multiplication operation:
// using normal image
// note that everything after the plus depends entirely on the image
out = current * (1-img.a) + vec4(img.r*img.a, img.g*img.a, img.b*img.a, img.a)
// using premultiplied image
out = current * (1-img.a) + img
Which might make sense if you're drawing same bitmap very many times.
Also premultiplication is just a way to cache the multiplication operation:
Which might make sense if you're drawing same bitmap very many times.