I have a possibly related problem with h264 on iPhone but with decoding instead of encoding. In my case the problem occurs with a streaming source that has Encoder set to H.264 or H.264B only (but not H264High). When the streaming source is encoded with H.264H (H.264high) the iPhone decodes the stream successfully. But when decoding in iOS simulator, it doesn't matter which of the 3 encodings is used by the source! Have you tried all 3 encodings in your project? I know this is a long shot but there is some similarity: Different results between physical iPhone versus simulator on h.264 streams.