These portable devices are usually very specific. We will not discuss therefore either operating system or resolution.
 
Device type Manufacturer/Model Remark
Portable player DVD/DivX portable player (car player or travel player) All these devices use the old DVD/DIVX format with anamorphic resolution 720x576 (PAL) or 720x480 ( NTSC).
Movie format is: Container: AVI - Video Codec: MPEG4 - Audio Codec: MP3
If the device does not have a USB port, burn a DVD from your video files. Otherwise simply copy your files to a USB pendrive.
iPod Classic (G5/G6)
iPod Nano (G3/G4/G5)
These two portable player were especially designed for music. Therefore, their resolution is only QVGA.
Movie format is: Container: MP4 - Video Codec: h264 - Audio Codec: AAC-LC
Apple iPod Touch This portable player has a video resolution comparable to the DVD (without anamorphism).
Movie format is: Container: MP4 - Video Codec: h264 - Audio Codec: AAC-LC
Portable LED/LCD TV These devices, when they support the HD TV, have a real resolution of 1024x576.
Movie format is: Container: MP4 - Video Codec: h264 - Audio Codec: AAC-LC
Handheld game console Sony PSP Resolution 320x480 / NTSC
-s 320x480 -b 512000 -ar 24000 -ab 64000 -f psp -r 29.97
-ac 2 -ar 48000 -acodec libfAAC-LC -ab 128k -r FRAME_RATE -s WIDTHxHEIGHT -vcodec libh264 -vpre slower -vpre main -level 21 -refs 2 -b BIT_RATE -bt BIT_RATE -aspect WIDTH:HEIGHT -f psp