Comment 2 for bug 1552245

Hello, the 2 videos are not the same : the file "dog.mp4" has no sound track in it and the aspect radio is different :
If this may help you, look at the technical data:

FILENAME : videos/dog.mp4
 Type : ISO Media, MPEG v4 system, version 1
 Size : 334 688 octet, 326.84 KiB - Date: 19700101.040000 - Duration: 00:00:10.879 (136 frames)
 Video : AVC MPEG-4 Codec/4cc:isom 462H(0x34363248) BR/Nom/Ov:244Kbps - 246Kbps Aspect:280x150 RatioDsp/Pix:1.867 1.000 VFRfps 8 4:2:0 Progr PPF

FILENAME : videos/sample.mp4
 Type : ISO Media, MPEG v4 system, version 1
 Size : 1 055 736 octet, 1 030.99 KiB, 1.00 MiB - Date: 19700101.040000 - Duration: 00:00:05.312 (132 frames)
 Video : AVC MPEG-4 Codec/4cc:isom 462H(0x34363248) BR/Nom/Ov:1206Kbps - VBRbps Aspect:1280x720 RatioDsp/Pix:1.778 1.000 CFRfps 8 4:2:0 Progr PPF
 Audio1: AAC LC VBR 384Kbps 6ch 48000Hz